LU-1361 build: enable kabi on rhel6

LU-1361 build: enable kabi on rhel6

Turn on USE_KABI=true to build with kabi on rhel6

Signed-off-by: Minh Diep <mdiep@whamcloud.com>
Change-Id: Ie028ced17baf5a4540c59b8b63fb279a146718a6
Reviewed-on: http://review.whamcloud.com/2642
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Tested-by: Hudson
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Brian J. Murrell <brian@whamcloud.com>
Tested-by: Brian J. Murrell <brian@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>