vcl: Centralize struct vcldir tear down

And doing so plug the director lock leak spotted by asan.

Refs 47586588
Refs 6e9b8d6d

bin/varnishd/cache/cache_vcl.c

@@ -457,11 +457,9 @@ vcl_KillBackends(struct vcl *vcl)
 		if (vdir == NULL)
 			break;
 		VTAILQ_REMOVE(&vcl->director_list, vdir, list);
-		REPLACE(vdir->cli_name, NULL);
 		AN(vdir->methods->destroy);
 		vdir->methods->destroy(vdir->dir);
-		FREE_OBJ(vdir->dir);
-		FREE_OBJ(vdir);
+		vcldir_free(vdir);
 	}
 	Lck_Unlock(&vcl_mtx);
 }

bin/varnishd/cache/cache_vcl.h

@@ -71,6 +71,7 @@ extern struct lock		vcl_mtx;
 extern struct vcl		*vcl_active; /* protected by vcl_mtx */
 struct vcl *vcl_find(const char *);
 void VCL_Update(struct vcl **, struct vcl *);
+void vcldir_free(struct vcldir *);
 
 struct vcltemp {
 	const char * const	name;

bin/varnishd/cache/cache_vrt_vcl.c

@@ -138,7 +138,7 @@ VCL_Rel(struct vcl **vcc)
 
 /*--------------------------------------------------------------------*/
 
-static void
+void
 vcldir_free(struct vcldir *vdir)
 {