tests: Change 'volume create' to 'volume create force'

Using 'force' when creating volumes prevents errors when creating bricks in the root partition. This fixes test bug-823081.t for bug-962226

Change-Id: I00996e1ab76713084076507d0aebdb65edc806c8
BUG: 962226
Signed-off-by: John Smith <lbalbalba@gmail.com>
Reviewed-on: http://review.gluster.org/5036
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Krutika Dhananjay <kdhananj@redhat.com>