ensure linuxbridge dependency is installed on RHEL

Package['neutron-plugin-linuxbridge'] is defined in
plugins/linuxbridge.pp but is missing in agents/linuxbridge.pp.

If agents::linuxbridge is used directly, the package is not defined.
This changes fixes the situation on RHEL.

The problem has already been fixed for OVS in
changeset Iedf8a607915f65b7a8cf7af99749b9b65cba7bd9

Change-Id: Ic4e15825e4f2d1f2ce2c34d2fdb01c8f6b19d491

manifests/agents/linuxbridge.pp

@@ -44,6 +44,13 @@ class neutron::agents::linuxbridge (
     # linuxbridge agent package. The configuration file for the linuxbridge
     # agent is provided by the neutron linuxbridge plugin package.
     Package['neutron-plugin-linuxbridge'] -> Neutron_plugin_linuxbridge<||>
+
+    if ! defined(Package['neutron-plugin-linuxbridge']) {
+      package { 'neutron-plugin-linuxbridge':
+        ensure  => $package_ensure,
+        name    => $::neutron::params::linuxbridge_server_package,
+      }
+    }
   }
 
   if $enable {

spec/classes/neutron_agents_linuxbridge_spec.rb

@@ -64,10 +64,17 @@ describe 'neutron::agents::linuxbridge' do
     end
 
     let :platform_params do
-      { :linuxbridge_agent_package => 'openstack-neutron-linuxbridge',
+      { :linuxbridge_server_package => 'openstack-neutron-linuxbridge',
         :linuxbridge_agent_service => 'neutron-linuxbridge-agent' }
     end
 
     it_configures 'neutron linuxbridge agent'
+
+    it 'installs neutron linuxbridge package' do
+      should contain_package('neutron-plugin-linuxbridge').with(
+        :ensure => params[:package_ensure],
+        :name   => platform_params[:linuxbridge_server_package]
+      )
+    end
   end
 end