nm: Install the .name file into /usr/lib/NetworkManager/VPN
It's the preferred location for system-provided plugins.
A compatible file in /etc is still kept. Also, the compatibility /etc
file needs to use a full path due to a bug in GNOME Shell.
The full path to a arch-dependent file in a supposedly arch-independent
file is a sin and a multilib violation in some distributions. However.
some pre-release versions of NetworkManager-1.2 as shipped by
distributions require a full path. Let's keep a configure-time option
for that.