Explicitly enable docker shared-pid for e2e_node

This also renames isSharedPIDNamespaceEnabled() to
isSharedPIDNamespaceSupported() to be more accurate.

test/e2e_node/docker_test.go

@@ -40,11 +40,11 @@ var _ = framework.KubeDescribe("Docker features [Feature:Docker]", func() {
 		It("processes in different containers of the same pod should be able to see each other", func() {
 			// TODO(yguo0905): Change this test to run unless the runtime is
 			// Docker and its version is <1.13.
-			By("Check whether shared PID namespace is enabled.")
-			isEnabled, err := isSharedPIDNamespaceEnabled()
+			By("Check whether shared PID namespace is supported.")
+			isEnabled, err := isSharedPIDNamespaceSupported()
 			framework.ExpectNoError(err)
 			if !isEnabled {
-				framework.Skipf("Skipped because shared PID namespace is not enabled.")
+				framework.Skipf("Skipped because shared PID namespace is not supported by this docker version.")
 			}
 
 			By("Create a pod with two containers.")

test/e2e_node/docker_util.go

@@ -43,9 +43,9 @@ func getDockerAPIVersion() (semver.Version, error) {
 	return semver.MustParse(version.APIVersion + ".0"), nil
 }
 
-// isSharedPIDNamespaceEnabled returns true if the Docker version is 1.13.1+
+// isSharedPIDNamespaceSupported returns true if the Docker version is 1.13.1+
 // (API version 1.26+), and false otherwise.
-func isSharedPIDNamespaceEnabled() (bool, error) {
+func isSharedPIDNamespaceSupported() (bool, error) {
 	version, err := getDockerAPIVersion()
 	if err != nil {
 		return false, err

test/e2e_node/services/kubelet.go

@@ -155,6 +155,7 @@ func (e *E2EServices) startKubelet() (*server, error) {
 		"--serialize-image-pulls", "false",
 		"--pod-manifest-path", manifestPath,
 		"--file-check-frequency", "10s", // Check file frequently so tests won't wait too long
+		"--docker-disable-shared-pid=false",
 		// Assign a fixed CIDR to the node because there is no node controller.
 		//
 		// Note: this MUST be in sync with with the IP in