Make sure ovs bridge is created before setting mac-table-size

After [1] puppet-ovn is setting mac-table-size using ovs-vsctl which
requires the bridge to exist in advance or it will fail.

[1] https://review.openstack.org/#/c/580114/

Change-Id: Ic54ec0bd81817982559e80bef1f152063073e5e5
(cherry picked from commit 17826fc88a)

manifests/controller.pp

@@ -123,7 +123,7 @@ class ovn::controller(
           command => "ovs-vsctl --timeout=5 set Bridge ${br} other-config:mac-table-size=${mac_table_size}",
           unless  => "ovs-vsctl get bridge ${br} other-config:mac-table-size | grep -q -w ${mac_table_size}",
           path    => '/usr/sbin:/usr/bin:/sbin:/bin',
-          require => Service['openvswitch']
+          require => [ Service['openvswitch'], Vs_bridge[$br] ],
         }
       }
     }