Fix the geofencing test to not break if the promises resolve asynchronously.

LayoutTests/http/tests/geofencing/resources/worker.js

+importScripts('../../serviceworker/resources/worker-test-harness.js');
+
+promise_test(function(test) {
+    return navigator.geofencing.registerRegion(
+        new CircularGeofencingRegion({latitude: 37.421999,
+                                      longitude: -122.084015}))
+      .then(test.unreached_func('Promise should not have resolved'))
+      .catch(function() { });
+  }, 'registerRegion should fail');
+
+promise_test(function(test) {
+    return navigator.geofencing.unregisterRegion("")
+      .then(test.unreached_func('Promise should not have resolved'))
+      .catch(function() { });
+  }, 'unregisterRegion should fail');
+
+promise_test(function(test) {
+    return navigator.geofencing.getRegisteredRegions()
+      .then(test.unreached_func('Promise should not have resolved'))
+      .catch(function() { });
+  }, 'getRegisteredRegions should fail');