Change the whole vty configuration for NS to be more flexible
and support more setups. Old configurations are invalid.
API change which must be synchronized with libosmocore
For further information see:
https://osmocom.org/projects/libosmocore/wiki/Network_service_(NS)
Depends-on: I8c3f2afecc74b78f7f914f7dce166cbcb63444eb (libosmocore)
Change-Id: Ie9306ab4d4738c2c57a69987086e22771b30657e