reduce default lease time to 5 minutes

Devstack used in development is about things coming and going
quickly. The long dhcp leases mean that we might miss a release, and
keep a stale lease around for way too long. See if this helps.

Change-Id: I9a58a4e64777f56ad7ec66242a319f985469469e

Author: sdague

lib/nova

@@ -689,6 +689,8 @@ function create_nova_conf_nova_network {
     iniset $NOVA_CONF DEFAULT public_interface "$PUBLIC_INTERFACE"
     iniset $NOVA_CONF DEFAULT vlan_interface "$VLAN_INTERFACE"
     iniset $NOVA_CONF DEFAULT flat_network_bridge "$FLAT_NETWORK_BRIDGE"
+    # force down dhcp leases to 5 minutes, which lets us expire faster
+    iniset $NOVA_CONF DEFAULT dhcp_lease_time 300
     if [ -n "$FLAT_INTERFACE" ]; then
         iniset $NOVA_CONF DEFAULT flat_interface "$FLAT_INTERFACE"
     fi