test: let web-audio-test-api resume

Without this change, `web-audio-test-api` can throw like this:

```
TypeError: Failed to execute the 'transitionToState' on 'AudioContext'

not enabled
```

Author: cwillisf

test/unit/util/audio-context.test.js

@@ -1,4 +1,9 @@
+/* global WebAudioTestAPI */
 import 'web-audio-test-api';
+WebAudioTestAPI.setState({
+    'AudioContext#resume': 'enabled'
+});
+
 import SharedAudioContext from '../../../src/lib/audio/shared-audio-context';
 
 describe('Shared Audio Context', () => {

test/unit/util/vm-manager-hoc.test.jsx

@@ -1,4 +1,8 @@
+/* global WebAudioTestAPI */
 import 'web-audio-test-api';
+WebAudioTestAPI.setState({
+    'AudioContext#resume': 'enabled'
+});
 
 import React from 'react';
 import configureStore from 'redux-mock-store';