Remove `auto_unmount` mount option from pv spec annotation to setup() func.

At present, `auto_unmount` option is recorded at PV annotation of glusterfs PV.
Due to the preference given in MountOptionFromSpec() for annotation mount options
over sc supplied mount options(Ref PR# https://github.com/kubernetes/kubernetes/pull/66576),
the sc supplied mount options are not honoured in glusterfs plugin
eventhough the driver returns `true` for storage class mountoptions
support at probe.

This patch removes `auto_unmount` option from annotation of the pv spec.

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

pkg/volume/glusterfs/glusterfs.go

@@ -322,7 +322,11 @@ func (b *glusterfsMounter) setUpAtInternal(dir string) error {
 		}
 
 	}
+
+	//Add backup-volfile-servers and auto_unmount options.
 	options = append(options, "backup-volfile-servers="+dstrings.Join(addrlist[:], ":"))
+	options = append(options, "auto_unmount")
+
 	mountOptions := volutil.JoinMountOptions(b.mountOptions, options)
 
 	// with `backup-volfile-servers` mount option in place, it is not required to
@@ -719,6 +723,7 @@ func (p *glusterfsVolumeProvisioner) Provision(selectedNode *v1.Node, allowedTop
 	if len(pv.Spec.AccessModes) == 0 {
 		pv.Spec.AccessModes = p.plugin.GetAccessModes()
 	}
+
 	pv.Spec.MountOptions = p.options.MountOptions
 
 	gidStr := strconv.FormatInt(int64(gid), 10)
@@ -728,7 +733,6 @@ func (p *glusterfsVolumeProvisioner) Provision(selectedNode *v1.Node, allowedTop
 		volutil.VolumeDynamicallyCreatedByKey: heketiAnn,
 		glusterTypeAnn:                        "file",
 		"Description":                         glusterDescAnn,
-		v1.MountOptionAnnotation:              "auto_unmount",
 		heketiVolIDAnn:                        volID,
 	}