scsi: scsi_transport_srp: Don't block target in failfast state

If the port is in SRP_RPORT_FAIL_FAST state when srp_reconnect_rport() is
entered, a transition to SDEV_BLOCK would be illegal, and a kernel WARNING
would be triggered. Skip scsi_target_block() in this case.

Link: https://lore.kernel.org/r/20210111142541.21534-1-mwilck@suse.com
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin Wilck <mwilck@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>