md_monitor: Enable option '-O'

Forgot to enable the corresponding short option for
'--open-file-limits'.

References: bnc#822149

Signed-off-by: Hannes Reinecke <hare@suse.de>
monitor_testcase_functions: Detect DASD layout

We should it issuing a 'CP Q USERID' to figure out which
DASD layout to use.

Signed-off-by: Hannes Reinecke <hare@suse.de>
monitor_testcase_5: Vary off path

We also need to vary off the path for the testcase to work
properly.

References: bnc#826106

Signed-off-by: Hannes Reinecke <hare@suse.de>