tests: Added function to generate brick statedump

Change-Id: I5f394a028a3251ec673c8787b2c67691a8b57449
BUG: 908146
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/4470
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>