libnm: avoid loosing signals

libnm: avoid loosing signals

D-Bus has an upper limit on number of Match rules and it's rather easy
to hit as the proxy likes to add one for each object. Let's remove the Match
rule the proxy added and ensure a less granular rule is present instead.

Ideally, we should be able to tell glib not to hook its rules.
Related: https://bugzilla.gnome.org/show_bug.cgi?id=758749

https://bugzilla.gnome.org/show_bug.cgi?id=758751