Changes

asterisk: pjsip.conf: Stop Asterisk doing unexpected REGISTER on IMS

REGISTER should only be done when the IMS APN is ready, and baseband
then interface asks it to register.

Change-Id: I56249d4138c0a1f5824e089c14c095badc41dc95

asterisk: pjsip.conf: Enable USIM Auth over AMI interface

Astersik_Tests already implement the related AMI procedures, hence
configure Asterisk to use them.

Depends: osmo-ttcn3-hacks.git ddc4c709e51b92dae4d10f0c71b062e4719da673
Change-Id: Iab2e9ad21ff6271ae51329608658ffe353173f38