gluster: Add force option to add brick command

Allows option to glusterfs to create brick directries
under root partition.

Change-Id: I907e3798d2a360cfcfd736d7cf9cb8f43c95ca10
Signed-off-by: Timothy Asir <tjeyasin@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/21525
Reviewed-by: Bala.FA <barumuga@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>