Also give the per-pool lock its own class

(see previous)

bin/varnishd/cache/cache_pool.c

@@ -146,7 +146,7 @@ pool_mkpool(unsigned pool_no)
 	AN(pp->a_stat);
 	pp->b_stat = calloc(1, sizeof *pp->b_stat);
 	AN(pp->b_stat);
-	Lck_New(&pp->mtx, lck_wq);
+	Lck_New(&pp->mtx, lck_perpool);
 
 	VTAILQ_INIT(&pp->idle_queue);
 	VTAILQ_INIT(&pp->poolsocks);

include/tbl/locks.h

@@ -40,6 +40,7 @@ LOCK(hcb)
 LOCK(lru)
 LOCK(mempool)
 LOCK(objhdr)
+LOCK(perpool)
 LOCK(pipestat)
 LOCK(probe)
 LOCK(sess)