This event runs before a connection/device is announced as
"activated" or "connected", to enable scripts to do things
before applications begin using connectivity.  For example,
this could be used to manage /etc/resolv.conf outside of
NetworkManager and ensure that resolv.conf had correct
information before DNS is used.

Note that this is different than the Debian or Gentoo "pre-up"
event used in /etc/network/interfaces, as that event runs before
any L2 configuration has started.  If we really need an event
like that, we'll add it later as "lower-up".