Fix error when receiving an already sent timestamp from VoE.

BUG=issue715
TEST=automatic rapid switching between 32 kHz stereo and 16 kHz mono codecs in voe_cmd_test does not repro.

Review URL: https://webrtc-codereview.appspot.com/712006

git-svn-id: http://webrtc.googlecode.com/svn/trunk@2547 4adac7df-926f-26a2-2b94-8c16560cd09d
1 file changed