Do not abort path verification when waiting for an interrupt timed out.
Use path_noirq_mask to keep track of the paths used for this (also
maintain a path_notoper_mask for debugging purposes). If the timeout
happend to be during an operation where we query or alter the state of
path groups set the pgid_unknown flag.

With this change we allow usage of devices which have such ill-behaved
paths (if at least one path is operational).
Reviewed-by: NPeter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: NSebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>