From: Martin Schwidefsky <schwidefsky@de.ibm.com>

Common i/o layer changes:
 - Delay unregister/register of ccw devices reappering on a different
   subchannel. Search for the old ccw_device & subchannel for the
   reattached device and deregister it too to avoid inconsistencies.
 - Fix path grouping for devices that present command reject for
   SetPGID but not for SensePGID.