LU-469 Build with lustre own kernel config file.

LU-469 Build with lustre own kernel config file.

-- Use lustre own rhel6 kernel config files in lbuild.
-- Rebase config files in latest vendor update.
-- Correct config file diff output.

Change-Id: I9ee5115009de5bcb00084dcac2e204774178a8c1
Signed-off-by: Yang Sheng <ys@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/1034
Tested-by: Hudson
Reviewed-by: Oleg Drokin <green@whamcloud.com>