redis: say whether it still holds a consumer's ACL user

The server keeps ACL users in memory only, so a restart forgets every
consumer while the provisioner keeps running (hq issue 120). holds()
checks ACL GETUSER for the user, enabled, with the mesh's password, so
the harness makes a forgotten user again. Needs mesh-sdk 0.1.1.

modules/redis/provisioner/index.ts

@@ -43,4 +43,11 @@ runProvisioner("redis-cache", {
     await redis.deleteAclUser(p.as);
     await announce("module.redis.cache.deprovisioned", { username: p.as });
   },
+
+  // This server keeps its ACL users in memory only, so a restart of it forgets every consumer while
+  // this provisioner keeps running. Asked every minute, so a forgotten user is made again instead
+  // of every consumer failing to authenticate in silence (novox/hq issue 120).
+  async holds(p: Provision): Promise<boolean> {
+    return redis.holdsAclUser(p.as, p.password);
+  },
 });