* removed nua_callstate_authenticating as it was never hit
* move debug statement further up, because we might not reach it if no
corresponding call is found
* handle 401 and 407 the same way
note: we should record which realm we're authenticating against during
REGISTER so we can prompt the user for additional credentials when
challenged for a different realm - still happens when calling from
a sip.linphone.org account to a jmp.bwapp.bwsip.io account.
17ac56fe44