rtcp-ice: fix setting of rtcp ICE component

RTCP default address might not be provided by peer in the
received SDP, leading to misconfiguration of RTCP ICE
socket. Now, when the RTCP default address is not present,
the RTP address will be used instead.
Note when ICE is used, the RTP/RTCP default addresses are
only needed to identify the underlying ICE socket.

Gitlab: #587

Change-Id: Ia16eb7d25407e67b6ab5a29c18fc3c56e6fc15aa