LU-7323 test: Unknown symbol mb_cache_create (err 0)" on RHEL7

LU-7323 test: Unknown symbol mb_cache_create (err 0)" on RHEL7

The error message is seen if mbcache module isn't loaded.

Before RHEL7 it was part of ext4, but EL7 have mbcache as
separate module and needs an extra `modprobe mbcache` command
before tests are run from local build dir.

This fixes the function load_modules_local() in test-framework.sh

Seagate-bug-id: MRP-3018
Change-Id: I7f1317355785c191287788bcb177d78b12231c97
Signed-off-by: Alexey Lyashkov <alexey.lyashkov@seagate.com>
Signed-off-by: Parinay Kondekar <parinay.kondekar@seagate.com>
Reviewed-on: http://review.whamcloud.com/16900
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Christopher J. Morrone <morrone2@llnl.gov>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>