REASSIGN OWNED: consider grants on tablespaces, too

Apparently this was considered in the original code (see commit
cec3b0a9) but I failed to notice that such entries would always be
skipped by the database check at the start of the loop.

Per bugs #7578 by Nikolay, #6116 by tushar.qa@gmail.com.

src/backend/catalog/pg_shdepend.c

@@ -1185,8 +1185,12 @@ shdepDropOwned(List *roleids, DropBehavior behavior)
 			InternalGrant istmt;
 			ObjectAddress obj;
 
-			/* We only operate on objects in the current database */
-			if (sdepForm->dbid != MyDatabaseId)
+			/*
+			 * We only operate on shared objects and objects in the current
+			 * database
+			 */
+			if (sdepForm->dbid != MyDatabaseId &&
+				sdepForm->dbid != InvalidOid)
 				continue;
 
 			switch (sdepForm->deptype)