Full HA->HA NG migration might fail setting maintenance-mode

Full HA->HA NG migration might fail setting maintenance-mode

Currently we do the following in the migration path:
pcs property set maintenance-mode=true
if ! timeout -k 10 300 crm_resource --wait; then
     echo_error "ERROR: cluster remained unstable after setting maintenance-mode for more than 300 seconds, exiting."
     exit 1
fi

crm_resource --wait can actually take forever under certain conditions.
The property will be set atomically across the cluster nodes so we should be good
without this.

Change-Id: I8f531d63479b81d65b572c4431c9db6f610f7e04
Closes-Bug: #1628393