LU-6707 test: load loop module to have loop devices

LU-6707 test: load loop module to have loop devices

Since there is no default loop device on EL7, load
loop module with option max_loop=8 to have loop devices
ready. posix.sh is not going to pass until LU-9102 get
resolved, but first fix the loop device issue.

Change-Id: I9fb9eba15099e5569dbc04fcd4454656a59fdd52
Signed-off-by: Wei Liu <wei3.liu@intel.com>
Reviewed-on: https://review.whamcloud.com/15130
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: James Nunez <james.a.nunez@intel.com>
Tested-by: Jenkins
Reviewed-by: Minh Diep <minh.diep@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>