LU-387 mmp.sh test_9 failed

LU-387 mmp.sh test_9 failed

The mmp.sh test_9 often fail for the script killing the e2fsck process
on wrong timing, so we use some tricky way to make sure the MMP block
stay in 'e2fsck' state before mounting the device.

Signed-off-by: Niu Yawei <niu@whamcloud.com>
Change-Id: I35a2f9708fa7dd3ea0cad246b767578209feeee3
Reviewed-on: http://review.whamcloud.com/991
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Hudson
Reviewed-by: Johann Lombardi <johann@whamcloud.com>