DHCP: delete config option dnsmasq_dns_server

This field was marked as deprecated In commit
a269541c60. That was in Kilo
which has provided enough time for admins to addjust to this.

In addition to this the patch sets the default value as [].
If a value is not specified this is None and that should not be
the default list.

DocImpact
UpgradeImpact

Change-Id: Ieaf18ffc9baf7e1caebe9de47017338bebd92c84

neutron/agent/dhcp/config.py

@@ -78,9 +78,9 @@ DNSMASQ_OPTS = [
                help=_('Override the default dnsmasq settings '
                       'with this file.')),
     cfg.ListOpt('dnsmasq_dns_servers',
+                default=[],
                 help=_('Comma-separated list of the DNS servers which will be '
-                       'used as forwarders.'),
-                deprecated_name='dnsmasq_dns_server'),
+                       'used as forwarders.')),
     cfg.StrOpt('dnsmasq_base_log_dir',
                help=_("Base log dir for dnsmasq logging. "
                       "The log contains DHCP and DNS log information and "

neutron/agent/linux/dhcp.py

@@ -390,10 +390,8 @@ class Dnsmasq(DhcpLocalProcess):
                    min(possible_leases, self.conf.dnsmasq_lease_max))
 
         cmd.append('--conf-file=%s' % self.conf.dnsmasq_config_file)
-        if self.conf.dnsmasq_dns_servers:
-            cmd.extend(
-                '--server=%s' % server
-                for server in self.conf.dnsmasq_dns_servers)
+        for server in self.conf.dnsmasq_dns_servers:
+            cmd.append('--server=%s' % server)
 
         if self.conf.dhcp_domain:
             cmd.append('--domain=%s' % self.conf.dhcp_domain)

releasenotes/notes/dnsmasq_dns_servers-d729c04887ce67b4.yaml

@@ -0,0 +1,5 @@
+---
+upgrade:
+  - The configuration option dnsmasq_dns_server was
+    deprecated in the kilo cycle. This value is no longer
+    supported.