rtspsrc: (network) timeout behaviour inconsistent between TCP and UDP

Submitted by Mark Nauwelaerts @mnauw

Link to original bug (#588144)

Description

rtspsrc's tcp_timeout property prevents rtspsrc from "hanging" if network timeout/interruption occurs during streaming (or interaction with RTSP server). However, no such (stringent) checks are performed when UDP happens to be selected (there may be some sender timeout detection in rtpbin/jitterbuffer, but the net overall effect/user experience is not quite the same).

Although this may or may not be intentional and/or related to UDP issues (e.g. inherently less reliable than TCP), possible patch follows anyway.