This makes package updates more robust, avoiding in-place replaces of
the plugins.

Previously, if an upgrade transaction was terminated, NetworkManager
library could end up being of a different version than the plugins.
If the user was unfortunate enough to connect using a connection that
required a plugin (say, Wi-Fi), he would be left without a network
connection making it somewhat inconvenient to recover from the botched
upgrade.

This makes the whole situation a little bit less sad.