deploy: Update /etc/default/snf-network tmpl

..to include constants introduced in 0.16.
Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>

snf-deploy/files/etc/default/snf-network

+STATE_DIR=/var/lib/snf-network
+LOGFILE=/var/log/ganeti/snf-network.log
+IFUP_EXTRA_SCRIPT=/etc/ganeti/ifup-extra
+
 MAC_MASK=ff:ff:f0:00:00:00
 
 TAP_CONSTANT_MAC=cc:47:52:4e:45:54 # GRNET in hex :-)