settings: pass valid error domain to g_set_error() in load_plugins()

glib asserts that the error domain parameter is a non-zero quark.

Signed-off-by: Thomas Haller <thaller@redhat.com>
contrib/rpm: do not override configuration files on updates (rh #1153901)

Rather leave modified configuration files untouched and save the new files
with .rpmnew suffix.

http://stackoverflow.com/questions/14511334/rpm-upgrade-handling-of-config-files

https://bugzilla.redhat.com/show_bug.cgi?id=1153901
libnm: fix NMActiveConnection:specific-object-path

NMActiveConnection:specific-object was renamed to
NMActiveConnection:specific-object-path in 677314c5, but it didn't
actually work, because of assumptions NMObject makes. Fix that.
nmtst: fix a bug in NMTST_VARIANT_EDITOR

NMTST_VARIANT_EDITOR would crash if you tried to drop different
properties (or two different settings).