app/model: Hub: Add ability to pass reject func.

app/model/Hub.js

@@ -39,13 +39,18 @@ class Hub {
     let indexLambda = index.bind(this)
     let unindexLambda = unindex.bind(this)
 
-    this.waitAsync = async (id, locations) => {
+    this.waitAsync = async (id, locations, rejectFunc) => {
       let promise = new Promise((resolve, reject) => {
         this.drivers[id] = {
           resolve: resolve,
           reject: reject
         }
 
+        // Pass reject function.
+        if (rejectFunc) {
+          rejectFunc(reject)
+        }
+
         // Index locations.
         indexLambda(id, locations)
       })