fix bug:issue_2

fix bug:issue_2(https://github.com/newOcean/webrtc-ios/issues/2) to make sure onICEServers: method will be incoked before onOpen method in APPRTCAppDelegate.
fix bug:issue_2

fix bug:issue_2(newOcean#2) to make sure onICEServers: method incoked before onOpen method in APPRTCAppDelegate.
Merge pull request #2 from YK-Unit/issue_2

fix bug:issue_2