When bitrate is updated, a check against 'lookahead' setting is done.
If 'lookahead' is enabled, the bitrate update is disabled.
We indeed used to observe crashes with nvenc when frequent bitrate
resettings were effected while lookahead option was enabled.
But recent tests have shown that the issue is gone.
As a result this commit allows 'lookahead' with bitrate live update.
Signed-off-by: pkv <pkv@obsproject.com>
e355a32066