cli: remove-brick no longer defaults to commit-force

Problem : When gluster volume remove-brick is executed with out any option, it
defaults to force commit which results in data loss.

Fix : remove-brick can not be executed with out explicit option, user needs to
provide the option in the command line else the command will throw back an usage
error.

Earlier usage : volume remove-brick <VOLNAME> [replica <COUNT>] <BRICK> ...
                [start|stop|status|commit|force]

Current usage : volume remove-brick <VOLNAME> [replica <COUNT>] <BRICK> ...
                <start|stop|status|commit|force>

Change-Id: I2a49131f782a6c0dcd03b4dc8ebe5907999b0b49
BUG: 1077682
Signed-off-by: Atin Mukherjee <amukherj@redhat.com>
Reviewed-on: http://review.gluster.org/7292
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Shyamsundar Ranganathan <sam.somari@gmail.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>