LU-11524 tests: fix sanity-sec test_31 for all situations

LU-11524 tests: fix sanity-sec test_31 for all situations

In case setupall() is called with server_only, this info must be
passed to init_param_vars(), and init_param_vars() must return
immediately. Otherwise, it will try to do client-specific tunings
(including quota settings) whereas no clients are mounted.

Modify cleanup_31() in sanity-sec so that client-specific
tunings are done via setupall().
Also make client umount more robust in test_31.

Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I2db17c139768d0842ff65ac8313a8e7d1484c4ef
Reviewed-on: https://review.whamcloud.com/33380
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>