Update conf.c

The default bridge configuration uses the backoff restart configuration, however this is not cleared if only a constant timeout is desired, causing it to always use the backoff configuration with a 30 second cap.

To trigger this error, use a bridge configuration with a constant timeout (e.g restart_timeout 5). Note that the timeout value is not honoured. 

Clear the backoff configuration when applying restart_timeout.

Signed-off-by: Trevor Luscombe <trevor.luscombe@gmail.com>