Provide an option to supply log-file mount option for gluster plugin.

At present, `log-file` location of glusterfs client mount is decided
by the plugin, however at times, users/admin want to configure log-file
of gluster fuse client process on their own in some setups. Even though they can pass log-file
mount option through storage class, before this patch glusterfs plugin
always discard it. This patch enable/give preference
to admin supplied log-file mount option if specified in storage class.
If the log-file mount option is incomplete or wrong, plugin fallback to the
location which is carved out by the combination of pvc and pod name.

Signed-off-by: Humble Chirammal <hchiramm@redhat.com>

pkg/volume/glusterfs/glusterfs.go

@@ -288,12 +288,27 @@ func (c *glusterfsUnmounter) TearDownAt(dir string) error {
 
 func (b *glusterfsMounter) setUpAtInternal(dir string) error {
 	var errs error
-
 	options := []string{}
+	hasLogFile := false
+	log := ""
+
 	if b.readOnly {
 		options = append(options, "ro")
+
 	}
 
+	// Check logfile has been provided by user, if provided, use that as the log file.
+	for _, userOpt := range b.mountOptions {
+		if dstrings.HasPrefix(userOpt, "log-file") {
+			glog.V(4).Infof("log-file mount option has provided")
+			hasLogFile = true
+			break
+		}
+	}
+
+	// If logfile has not been provided, create driver specific log file.
+	if !hasLogFile {
+		log = ""
 		p := path.Join(b.glusterfs.plugin.host.GetPluginDir(glusterfsPluginName), b.glusterfs.volName)
 		if err := os.MkdirAll(p, 0750); err != nil {
 			return fmt.Errorf("failed to create directory %v: %v", p, err)
@@ -302,9 +317,13 @@ func (b *glusterfsMounter) setUpAtInternal(dir string) error {
 		// adding log-level ERROR to remove noise
 		// and more specific log path so each pod has
 		// its own log based on PV + Pod
-	log := path.Join(p, b.pod.Name+"-glusterfs.log")
-	options = append(options, "log-level=ERROR")
+		log = path.Join(p, b.pod.Name+"-glusterfs.log")
+
+	}
+
+	// Use derived/provided log file in gluster fuse mount
 	options = append(options, "log-file="+log)
+	options = append(options, "log-level=ERROR")
 
 	var addrlist []string
 	if b.hosts == nil {