tests: Modified test to use remove-brick instead of 'start' variant

        Backport of change f75be77 from master

remove-brick start doesn't remove the brick from the volume immediately.
It would wait until migration of data to other bricks are complete. Even
when there is no data to be migrated, one can expect a finite delay from
the time of remove-brick start command's exit and removal of brick(s).
This may cause subsequent checks on brick count to fail in a
non-deterministic manner.

Also, renamed the test file name to reflect bug-id corresponding to
community release.

BUG: 878004
Change-Id: Ic6e1360ae5a5280d0d7efe8c3e9a0aa57dddb508
Signed-off-by: Kaushal M <kaushal@redhat.com>
Reviewed-on: http://review.gluster.org/5052
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>