[SCSI] zfcp: Do not wait for SBALs on stopped queue
Trying to read the FC host statistics on an offline adapter results in
a 5 seconds wait. Reading the statistics tries to issue an exchange
port data request which first waits up to 5 seconds for an entry in
the request queue.
Change the strategy for getting a free SBAL to exit when the queue is
stopped. Reading the statistics will then fail without the wait.