Add vsc for requested and needed sizes for mempool.

Fix sess mempool names

bin/varnishd/cache/cache_mempool.c

@@ -80,6 +80,8 @@ mpl_alloc(const struct mempool *mpl)
 	AN(mi);
 	mi->magic = MEMITEM_MAGIC;
 	mi->size = tsz;
+	mpl->vsc->sz_wanted = tsz;
+	mpl->vsc->sz_needed = tsz + sizeof *mi;
 	return (mi);
 }
 

bin/varnishd/cache/cache_session.c

@@ -318,6 +318,7 @@ SES_NewPool(struct pool *wp, unsigned pool_no)
 	bprintf(nb, "req%u", pool_no);
 	pp->mpl_req = MPL_New(nb, &cache_param->req_pool,
 	    &cache_param->workspace_client);
+	bprintf(nb, "sess%u", pool_no);
 	pp->mpl_sess = MPL_New(nb, &cache_param->sess_pool, &ses_size);
 	return (pp);
 }