scsi_dh_alua: uninitialized variable in alua_rtpg()

BugLink: https://bugs.launchpad.net/bugs/1720228

It's possible to use "err" without initializing it.  If it happens to be
a 2 which is SCSI_DH_RETRY then that could cause a bug.  Bart Van Assche
pointed out that we should probably re-initialize it for every iteration
through the retry loop.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Hannes Reinicke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: James Bottomley <jejb@linux.vnet.ibm.com>
(cherry picked from commit a4bd8520)
Signed-off-by: Dragan Stancevic <dragan.stancevic@canonical.com>
Acked-by: Kleber Souza <kleber.souza@canonical.com>
Acked-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

drivers/scsi/device_handler/scsi_dh_alua.c

@@ -531,6 +531,7 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 		return SCSI_DH_DEV_TEMP_BUSY;
 
  retry:
+	err = 0;
 	retval = submit_rtpg(sdev, buff, bufflen, &sense_hdr, pg->flags);
 
 	if (retval) {