md_monitor: Check array for CLI message 'ArrayStatus'

The 'ArrayStatus' CLI message might race with MD shutdown,
so we need to update the device status.

Signed-off-by: Hannes Reinecke <hare@suse.de>
monitor_testcase_functions: Compare array states on exit

When we call 'stop_md' we should check the array status
with the original state to check if the status has changed.

Signed-off-by: Hannes Reinecke <hare@suse.de>
monitor_testcase_1: Checkpointing

Add checkpoint messages to compare the individual states
and abort if anything changed.

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