Srtpdec drop buffers

Submitted by avbahno

Link to original bug (#796171)

Description

I launch srtpenc/srtpdec examples, and can't get working stream
gst-launch-1.0 udpsrc port=5004 caps='application/x-srtp, payload=(int)8, ssrc=(uint)1356955624, srtp-key=(buffer)012345678901234567890123456789012345678901234567890123456789, srtp-cipher=(string)aes-128-icm, srtp-auth=(string)hmac-sha1-80, srtcp-cipher=(string)aes-128-icm, srtcp-auth=(string)hmac-sha1-80, roc=(uint)0' ! srtpdec ! rtppcmadepay ! alawdec ! pulsesink

Gst-launch-1.0 audiotestsrc ! alawenc ! rtppcmapay ! 'application/x-rtp, payload=(int)8, ssrc=(uint)1356955624' ! srtpenc key="012345678901234567890123456789012345678901234567890123456789" ! udpsink port=5004

Warning messages -
Could not get caps for stream with SSRC ...
Invalid buffer, dropping

Version: 1.14.0