Re-enable NetEqExternalDecoderTest for Android

The test runs without problems now.

BUG=3343
R=tina.legrand@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/16519005

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6144 4adac7df-926f-26a2-2b94-8c16560cd09d