network: fix rtp packet length

When sending rtp packets sizeof(buf) is used as length. This causes
all RTP packets to be the size of the buffer (4096) containing the
rtp payload and random excess data from previoes memory usage

Use the actual length of the received RTP data, rather then the
full buffer size.

Change-Id: I47a15701f9a7e7a492df183b67ec971f5be61069
1 file changed