Retry video RTP bind if port is taken.

[coreyfarrell]

Fixes #276

[coreyfarrell]

This patch can be tested by running the following python:

from socket import *
s = socket(AF_INET, SOCK_DGRAM)
s.bind(('', 6002))

Then run a sipp scenario without designating a specific media port. Assuming UDP/6000 is available it will pick that for audio RTP, then try and fail UDP/6002 for video RTP. Current code exits with failure, my patch causes it to close both sockets and start over at the next media port (without resetting the retry count). I verified this patch using the Asterisk testsuite tests/channels/SIP/sip_hold with the python script holding UDP/6002 in the background.

[wdoekes]

Thanks for the patch!

Not so fond of the commando pattern with the goto and +=3 though. So I rewrote it a bit. Please try c1158cf (fix/3.5/retry-video-port-276).

[coreyfarrell]

@wdoekes updated patch works for me and I agree it looks better without the goto. Do you want me to close this PR or are you going to update it?

[wdoekes]

Thanks for testing. We can close this and I'll merge my branch.