Fix relcache invalidation when relfilelocator is updated

In commit af0e7de, I removed a call to RelationCloseSmgr(), because
the dangling SMgrRelation was no longer an issue. However, we still
need the call when the relation's relfilelocator changes, so that the
new relfilelocator takes effect immediately.

Reported-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: https://www.postgresql.org/message-id/987b1c8c-8c91-4847-ca0e-879f421680ff%40gmail.com

Author: hlinnaka

src/backend/utils/cache/relcache.c

@@ -3060,7 +3060,10 @@ RelationCacheInvalidate(bool debug_discard)
 			 * map doesn't involve any access to relcache entries.
 			 */
 			if (RelationIsMapped(relation))
+			{
+				RelationCloseSmgr(relation);
 				RelationInitPhysicalAddr(relation);
+			}
 
 			/*
 			 * Add this entry to list of stuff to rebuild in second pass.