rtmpproto: Ignore errors from the getStreamLength method

It is never an error if this method failed. If rt->live was
explicitly set to 0 (known to be a recorded file), print it
as a warning, otherwise print it as a debug message.

Based on a patch by Michael Niedermayer.

Signed-off-by: Martin Storsjö <martin@martin.st>
Merge commit 'a490391157dcf4dc6b65352ec3eea2781dd0a404'

* commit 'a490391157dcf4dc6b65352ec3eea2781dd0a404':
  rtmpproto: Ignore errors from the getStreamLength method

Conflicts:
	libavformat/rtmpproto.c

See: 09711545f5d256bd3ac77004d123dae36c5db8f9
Merged-by: Michael Niedermayer <michaelni@gmx.at>
avformat/udp: UDP-Lite (RFC 3828) support added

(This fixes ticket #1501)

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>