Hang up only when we're in TRANSMITTING mode
Hang up only when we're in TRANSMITTING mode

When f->av.state equals TRANSMITTING, it means that we're neither
receiving, nor sending data, thus, we can cancel the call.

This doesn't apply to RINGING mode because this state is possible when
someone calls us, and we didn't answer yet.

cmotc/ratox,cmotc/ratox,pranomostro/ratox,pranomostro/ratox