Fix AMF selection fallback by PLMN ID when no UE identity is present or matching
If a mask is present (i.e., not zero), AMF selection by PLMN ID may still fail, causing the AMF selection process to skip the fallback option, i.e. selection by PLMN ID, when no UE identity is available or when no match is found.
This MR adds also warnings in case there's a match for the AMF is not found.
Edited by Guido Casati