network: fix network driver startup for qemu:///session

network: fix network driver startup for qemu:///session

This should resolve https://bugzilla.redhat.com/show_bug.cgi?id=958907

Recent new addition of code to read/write active network state to the
NETWORK_STATE_DIR in the network driver broke startup for
qemu:///session. The network driver had several state file paths
hardcoded to /var, which could never possibly work in session mode.

This patch modifies *all* state files to use a variable string that is
set differently according to whether or not we're running
privileged. (It turns out that logDir was never used, so it's been
completely eliminated.)

There are very definitely other problems preventing dnsmasq and radvd
from running in non-privileged mode, but it's more consistent to have
the directories used by them be determined in the same fashion.

NB: I've noted before that the network driver is storing its state
(including dnsmasq and radvd state) in /var/lib, while qemu stores its
state in /var/run. It would probably have been better if the two
matched, but it's been this way for a long time, and changing it would
break running installations during an upgrade, so it's best to just
leave it as it is.