Work around several issues with non-compliant RTSP servers.

In this particular case these RTSP servers were implemented as local services,
retransmitting live streams via a local RTSP server instance.

They picked wrong rtp/rtcp port pairs (odd rtp port), blank lines in the session
description, wrong case of the format description, relative base URLs...

Change-Id: I63fa90ca2398f19e8b52c147248bd2c5c2372426
related-to-bug: 3452103