glusterd: fix error in remove-brick-replica validation

Problem:
Reducing replica count of a volume using remove-brick command fails
if bricks are specified in a random order.

Fix: Modify subvol_matcher_verify() to permit order agnostic
replica count reduction.


Change-Id: I1f3d33e82a70d9b69c297f69c4c1b847937d1031
BUG: 1040408
Signed-off-by: Ravishankar N <ravishankar@redhat.com>
Reviewed-on: http://review.gluster.org/6489
Reviewed-by: Krishnan Parthasarathi <kparthas@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>