Run a portal's cleanup hook immediately when pushing it to FAILED state.

This extends the changes of commit 6252c4f9e2
so that we run the cleanup hook earlier for failure cases as well as
success cases.  As before, the point is to avoid an assertion failure from
an Assert I added in commit a874fe7b4c, which
was meant to check that no user-written code can be called during portal
cleanup.  This fixes a case reported by Pavan Deolasee in which the Assert
could be triggered during backend exit (see the new regression test case),
and also prevents the possibility that the cleanup hook is run after
portions of the portal's state have already been recycled.  That doesn't
really matter in current usage, but it foreseeably could matter in the
future.

Back-patch to 9.1 where the Assert in question was added.

src/backend/commands/portalcmds.c

@@ -224,7 +224,7 @@ PerformPortalClose(const char *name)
 	}
 
 	/*
-	 * Note: PortalCleanup is called as a side-effect
+	 * Note: PortalCleanup is called as a side-effect, if not already done.
 	 */
 	PortalDrop(portal, false);
 }
@@ -234,6 +234,10 @@ PerformPortalClose(const char *name)
  *
  * Clean up a portal when it's dropped.  This is the standard cleanup hook
  * for portals.
+ *
+ * Note: if portal->status is PORTAL_FAILED, we are probably being called
+ * during error abort, and must be careful to avoid doing anything that
+ * is likely to fail again.
  */
 void
 PortalCleanup(Portal portal)
@@ -420,7 +424,7 @@ PersistHoldablePortal(Portal portal)
 	PG_CATCH();
 	{
 		/* Uncaught error while executing portal: mark it dead */
-		portal->status = PORTAL_FAILED;
+		MarkPortalFailed(portal);
 
 		/* Restore global vars and propagate error */
 		ActivePortal = saveActivePortal;