sessions.

This type is used in RTP/ASF (served by WMS servers), and is required to
make UDP sessions work, but breaks TCP sessions. Therefore, we disable setup
for application streams in TCP/WMS streams.

See discussion in "[PATCH] RTSP-MS 8/15: fix RTSP-MS UDP" thread.

Originally committed as revision 17776 to svn://svn.ffmpeg.org/ffmpeg/trunk