ibmvscsis: Clear left-over abort_cmd pointers

With the addition of ibmvscsis->abort_cmd pointer within
commit 25e78531 ("ibmvscsis: Do not send aborted task response"),
make sure to explicitly NULL these pointers when clearing
DELAY_SEND flag.

Do this for two cases, when getting the new new ibmvscsis
descriptor in ibmvscsis_get_free_cmd() and before posting
the response completion in ibmvscsis_send_messages().
Signed-off-by: Bryant G. Ly <bryantly@linux.vnet.ibm.com>
Reviewed-by: Michael Cyr <mikecyr@linux.vnet.ibm.com>
Cc: <stable@vger.kernel.org> # v4.8+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c

@@ -1170,6 +1170,8 @@ static struct ibmvscsis_cmd *ibmvscsis_get_free_cmd(struct scsi_info *vscsi)
 		cmd = list_first_entry_or_null(&vscsi->free_cmd,
 					       struct ibmvscsis_cmd, list);
 		if (cmd) {
+			if (cmd->abort_cmd)
+				cmd->abort_cmd = NULL;
 			cmd->flags &= ~(DELAY_SEND);
 			list_del(&cmd->list);
 			cmd->iue = iue;
@@ -1774,6 +1776,7 @@ static void ibmvscsis_send_messages(struct scsi_info *vscsi)
 				if (cmd->abort_cmd) {
 					retry = true;
 					cmd->abort_cmd->flags &= ~(DELAY_SEND);
+					cmd->abort_cmd = NULL;
 				}
 
 				/*