If test calls RTPEM_bind twice, the previous socket is kept open
(ConnId 1) while the new one is assigned to the the expected ConnId for
RTP/RTCP packets received (ConnId), however, if remote was already
sending packets, it may happen that the port still receives those with
ConnId=1, which may make test fail with message:
"Received unexpected type from RTP"
Change-Id: I73f4af4e590dd3958e3f4d1dba0496c0750d642d