scsi_transport_srp: Block rport upon TL error even with fast_io_fail_tmo = off

The current behavior of the SRP transport layer when a transport layer
error is encountered is to block SCSI command processing only if
fast_io_fail_tmo != off.  The current behavior of the FC transport
layer when a transport layer error is encountered is to block SCSI
command processing no matter which value fast_io_fail_tmo has been set
to.  Make the behavior of the SRP transport layer consistent with that
of the FC transport layer to avoid confusion.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Roland Dreier <roland@purestorage.com>