[SIP SIMPLE client] sip-register hangs

[Juha Heinanen]

> after problems with blink, i tried cli sip clients (sipclients 0.15.0)
> and now also sip-register after registering hangs the console where it
> is started.  if i press control-d, q, return, etc., nothing happens.

actually, if i press control-c, the program terminates,
but if i first press control-d, nothing happens and after that even
control-c does not terminate the program.

-- juha