LU-2448 build: add {prepare-,}commit-msg git hooks

LU-2448 build: add {prepare-,}commit-msg git hooks

Add commit message and patch format hooks for b2_1 to match other
development branches.  This avoids problems when checking out b2_1
from master, where the .git/hooks/{prepare-,}commit-msg symlinks
are installed but not pointing at anything.

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: I9bea14402d1f5668855b55230aaac919e5d0d90e
Reviewed-on: http://review.whamcloud.com/4782
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>