Fix Wrong syntax for set:tag in dnsmasq startup option

Looks like the introduction of quotes in fix for previous
bug 1012443 was erroneous.

Fixes LP# 1152504

Change-Id: Ic84739e38e3b3567f1617302a33623de03196f85
(cherry picked from commit d8188ef)

nova/network/linux_net.py

@@ -870,7 +870,7 @@ 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,%ss' %
                          (network_ref['label'],
                           network_ref['dhcp_start'],
                           FLAGS.dhcp_lease_time),