Check and wait to avoid large replication lag in heap_multi_insert()

Reviewed-by: NAsim R P <apraveen@pivotal.io>
Reviewed-by: NHeikki Linnakangas <hlinnakangas@pivotal.io>
Reviewed-by: NPaul Guo <pguo@pivotal.io>
(cherry picked from commit eae1c6ef)

src/backend/access/heap/heapam.c

@@ -2940,6 +2940,9 @@ heap_multi_insert(Relation relation, HeapTuple *tuples, int ntuples,
 		tuples[i]->t_self = heaptuples[i]->t_self;
 
 	pgstat_count_heap_insert(relation, ntuples);
+
+	if (needwal)
+		wait_to_avoid_large_repl_lag();
 }
 
 /*