Allow to skip fsGroup chown on kubernetes

With this patch it's possible to disable fsGroup
kubernetes/kubernetes#68680
it is also merged on OKD openshift/origin#21070 3.11.x

Fix gluster#23

glfs-subvol/glfs-subvol

@@ -64,7 +64,7 @@ function doInit() {
     if [[ "x$msg" != "x" ]] ; then
         result="{\"status\": \"Failure\", \"message\": \"${msg}\"}"
     else
-        result="{\"status\": \"Success\", \"capabilities\": {\"attach\": false, \"selinuxRelabel\": false}}"
+        result="{\"status\": \"Success\", \"capabilities\": {\"attach\": false, \"selinuxRelabel\": false, \"fsGroup\": false}}"
     fi
     retResult $RC_OK "$result"
 }