Adding netmask to dnsmasq argument --dhcp-range

By default, dnsmasq will try to guess the proper subnet size but
sometimes it will fail. This patch provides the network netmask
to dnsmasq via the --dhcp-range argument.

Fixes: bug #1154929

Change-Id: I74d62c837b5310004b9151851697e3ea3b475f92
(cherry picked from commit fb151b5)

nova/network/linux_net.py

@@ -870,9 +870,10 @@ def restart_dhcp(context, dev, network_ref):
            '--pid-file=%s' % _dhcp_file(dev, 'pid'),
            '--listen-address=%s' % network_ref['dhcp_server'],
            '--except-interface=lo',
-           '--dhcp-range=set:%s,%s,static,%ss' %
+           '--dhcp-range=set:%s,%s,static,%s,%ss' %
                          (network_ref['label'],
                           network_ref['dhcp_start'],
+                          network_ref['netmask'],
                           FLAGS.dhcp_lease_time),
            '--dhcp-lease-max=%s' % len(netaddr.IPNetwork(network_ref['cidr'])),
            '--dhcp-hostsfile=%s' % _dhcp_file(dev, 'conf'),