Fix lint warnings for useless err checks.

This check was recently added to golint.

cmd/kubeadm/app/cmd/upgrade/apply.go

@@ -241,10 +241,7 @@ func PerformStaticPodUpgrade(client clientset.Interface, waiter apiclient.Waiter
 		return err
 	}
 
-	if err := upgrade.StaticPodControlPlane(waiter, pathManager, internalcfg); err != nil {
-		return err
-	}
-	return nil
+	return upgrade.StaticPodControlPlane(waiter, pathManager, internalcfg)
 }
 
 // DryRunStaticPodUpgrade fakes an upgrade of the control plane
@@ -268,8 +265,5 @@ func DryRunStaticPodUpgrade(internalcfg *kubeadmapi.MasterConfiguration) error {
 		files = append(files, dryrunutil.NewFileToPrint(realPath, outputPath))
 	}
 
-	if err := dryrunutil.PrintDryRunFiles(files, os.Stdout); err != nil {
-		return err
-	}
-	return nil
+	return dryrunutil.PrintDryRunFiles(files, os.Stdout)
 }

cmd/kubeadm/app/phases/addons/proxy/proxy.go

@@ -99,10 +99,7 @@ func CreateServiceAccount(client clientset.Interface) error {
 
 // CreateRBACRules creates the essential RBAC rules for a minimally set-up cluster
 func CreateRBACRules(client clientset.Interface) error {
-	if err := createClusterRoleBindings(client); err != nil {
-		return err
-	}
-	return nil
+	return createClusterRoleBindings(client)
 }
 
 func createKubeProxyAddon(configMapBytes, daemonSetbytes []byte, client clientset.Interface) error {
@@ -122,10 +119,7 @@ func createKubeProxyAddon(configMapBytes, daemonSetbytes []byte, client clientse
 	}
 
 	// Create the DaemonSet for kube-proxy or update it in case it already exists
-	if err := apiclient.CreateOrUpdateDaemonSet(client, kubeproxyDaemonSet); err != nil {
-		return err
-	}
-	return nil
+	return apiclient.CreateOrUpdateDaemonSet(client, kubeproxyDaemonSet)
 }
 
 func createClusterRoleBindings(client clientset.Interface) error {

cmd/kubeadm/app/phases/certs/pkiutil/pki_helpers.go

@@ -76,11 +76,7 @@ func WriteCertAndKey(pkiPath string, name string, cert *x509.Certificate, key *r
 		return err
 	}
 
-	if err := WriteCert(pkiPath, name, cert); err != nil {
-		return err
-	}
-
-	return nil
+	return WriteCert(pkiPath, name, cert)
 }
 
 // WriteCert stores the given certificate at the given location

pkg/kubelet/kubeletconfig/checkpoint/store/fsstore.go

@@ -56,10 +56,7 @@ func (s *fsStore) Initialize() error {
 	if err := utilfiles.EnsureFile(s.fs, filepath.Join(s.checkpointsDir, curFile)); err != nil {
 		return err
 	}
-	if err := utilfiles.EnsureFile(s.fs, filepath.Join(s.checkpointsDir, lkgFile)); err != nil {
-		return err
-	}
-	return nil
+	return utilfiles.EnsureFile(s.fs, filepath.Join(s.checkpointsDir, lkgFile))
 }
 
 func (s *fsStore) Exists(uid string) (bool, error) {
@@ -77,10 +74,7 @@ func (s *fsStore) Save(c checkpoint.Checkpoint) error {
 		return err
 	}
 	// save the file
-	if err := utilfiles.ReplaceFile(s.fs, filepath.Join(s.checkpointsDir, c.UID()), data); err != nil {
-		return err
-	}
-	return nil
+	return utilfiles.ReplaceFile(s.fs, filepath.Join(s.checkpointsDir, c.UID()), data)
 }
 
 func (s *fsStore) Load(uid string) (checkpoint.Checkpoint, error) {

pkg/kubelet/kubeletconfig/configfiles/configfiles_test.go

@@ -37,10 +37,7 @@ func addFile(fs utilfs.Filesystem, path string, file string) error {
 	if err := utilfiles.EnsureDir(fs, filepath.Dir(path)); err != nil {
 		return err
 	}
-	if err := utilfiles.ReplaceFile(fs, path, []byte(file)); err != nil {
-		return err
-	}
-	return nil
+	return utilfiles.ReplaceFile(fs, path, []byte(file))
 }
 
 func TestLoad(t *testing.T) {

pkg/kubelet/kubeletconfig/controller.go

@@ -248,10 +248,7 @@ func (cc *Controller) StartSync(client clientset.Interface, nodeName string) {
 func (cc *Controller) initialize() error {
 	utillog.Infof("ensuring filesystem is set up correctly")
 	// initialize local checkpoint storage location
-	if err := cc.checkpointStore.Initialize(); err != nil {
-		return err
-	}
-	return nil
+	return cc.checkpointStore.Initialize()
 }
 
 // localConfig returns the initConfig if it is loaded, otherwise returns the defaultConfig.

pkg/kubelet/kubeletconfig/util/files/files.go

@@ -109,10 +109,7 @@ func ReplaceFile(fs utilfs.Filesystem, path string, data []byte) error {
 		return err
 	}
 	// rename over existing file
-	if err := fs.Rename(tmpPath, path); err != nil {
-		return err
-	}
-	return nil
+	return fs.Rename(tmpPath, path)
 }
 
 // DirExists returns true if a directory exists at `path`, false if `path` does not exist, otherwise an error
@@ -138,8 +135,5 @@ func EnsureDir(fs utilfs.Filesystem, path string) error {
 	} // Assert: dir does not exist
 
 	// create the dir
-	if err := fs.MkdirAll(path, defaultPerm); err != nil {
-		return err
-	}
-	return nil
+	return fs.MkdirAll(path, defaultPerm)
 }

staging/src/k8s.io/client-go/util/cert/io.go

@@ -66,10 +66,7 @@ func WriteCert(certPath string, data []byte) error {
 	if err := os.MkdirAll(filepath.Dir(certPath), os.FileMode(0755)); err != nil {
 		return err
 	}
-	if err := ioutil.WriteFile(certPath, data, os.FileMode(0644)); err != nil {
-		return err
-	}
-	return nil
+	return ioutil.WriteFile(certPath, data, os.FileMode(0644))
 }
 
 // WriteKey writes the pem-encoded key data to keyPath.
@@ -80,10 +77,7 @@ func WriteKey(keyPath string, data []byte) error {
 	if err := os.MkdirAll(filepath.Dir(keyPath), os.FileMode(0755)); err != nil {
 		return err
 	}
-	if err := ioutil.WriteFile(keyPath, data, os.FileMode(0600)); err != nil {
-		return err
-	}
-	return nil
+	return ioutil.WriteFile(keyPath, data, os.FileMode(0600))
 }
 
 // LoadOrGenerateKeyFile looks for a key in the file at the given path. If it