delete routes and addresses when it quits. This causes those routes
and addresses to stick around forever, since dhcpcd won't delete
them when it runs next (even if it acquires a new lease on the same
interface). This is bad; in particular the stale (default) routes
can break networking.
The downside to removing "persistent" is that you should never ever
do "stop dhcpcd" on a remote machine configured by dhcpcd.
svn path=/nixos/trunk/; revision=33388