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

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.

Change-Id: Ic43f011e251640decb68e46f4a10e0824ade0ac9
BUG: 878004
Signed-off-by: Krishnan Parthasarathi <kparthas@redhat.com>
Reviewed-on: http://review.gluster.org/4885
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>