libnma/pygobject: libnma/NMA must use libnm/NM instead of legacy libraries

libnma uses libnm, and not libnm-util/libnm-glib. Hence, the python bindings
must load "NM" and not "NMClient"/"NetworkManager".

As it was, the generated bindings for libnma were unusable and loading
them would fail with

    libnm-ERROR **: libnm-util symbols detected; Mixing libnm with libnm-util/libnm-glib is not supported

https://bugzilla.gnome.org/show_bug.cgi?id=779153

Fixes: 76a12bea