cephfs: add locks for volumegroup

Adding a lock for the volumegroup so
that we can take care of serializing
the same requests to ensure same requests
are not served in parallel.

Signed-off-by: Madhu Rajanna <madhupr007@gmail.com>

internal/cephfs/driver.go

@@ -67,6 +67,7 @@ func NewControllerServer(d *csicommon.CSIDriver) *ControllerServer {
 		DefaultControllerServer: csicommon.NewDefaultControllerServer(d),
 		VolumeLocks:             util.NewVolumeLocks(),
 		SnapshotLocks:           util.NewVolumeLocks(),
+		VolumeGroupLocks:        util.NewVolumeLocks(),
 		OperationLocks:          util.NewOperationLock(),
 	}
 }