iscsi-target: Fix iscsit_get_tpg_from_np tpg_state bug

This patch fixes a bug in iscsit_get_tpg_from_np() where the
tpg->tpg_state sanity check was looking for TPG_STATE_FREE,
instead of != TPG_STATE_ACTIVE.

The latter is expected during a normal TPG shutdown once the
tpg_state goes into TPG_STATE_INACTIVE in order to reject any
new incoming login attempts.

Cc: <stable@vger.kernel.org> #3.10+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/iscsi/iscsi_target_tpg.c

@@ -137,7 +137,7 @@ struct iscsi_portal_group *iscsit_get_tpg_from_np(
 	list_for_each_entry(tpg, &tiqn->tiqn_tpg_list, tpg_list) {
 
 		spin_lock(&tpg->tpg_state_lock);
-		if (tpg->tpg_state == TPG_STATE_FREE) {
+		if (tpg->tpg_state != TPG_STATE_ACTIVE) {
 			spin_unlock(&tpg->tpg_state_lock);
 			continue;
 		}