engine : Refactored gluster volume profile VdsCommand

This patch refactors the volume profile vds command
to take an additional boolean parameter nfs which
helps to query the glusterfs for 2 types of stats
nfs and brick profile stats

Change-Id: I26cda9f8603e77296720f2dc062b94d5c10e7fd1
Signed-off-by: Anmol Babu <anbabu@redhat.com>