acceptance: enable lbaas service provider

We're testing neutron lbaas.
Since Mitaka [1], we need to load service_provider because the default
value is empty.

We could change the default value of service_providers in
manifests/services/lbaas.pp but that would not fit with what upstream
default in Neutron.

So this patch aims to:
* modify beaker manifests to load HAproxy service provider so LBaaS can
  work.
* add more documentation about it so people who hit this bug will easily
  debug and know they need to pass a service_provider.

[1] d13d53bce7 (diff-f9ccf8f7f0532acb2963d5d00f42dc15L64)

Partial-Bug: #1535382
Change-Id: Ia522a0d6b03aa00939a93d18b74862cf760cdd06

manifests/services/lbaas.pp

@@ -28,6 +28,10 @@
 #
 # [*service_providers*]
 #   (optional) Array of allowed service types or '<SERVICE DEFAULT>'.
+#   Note: The default upstream value is empty.
+#         If you plan to activate LBaaS service, you'll need to set this
+#         parameter otherwise neutron-server won't start correctly.
+#         See https://bugs.launchpad.net/puppet-neutron/+bug/1535382/comments/1
 #   Must be in form <service_type>:<name>:<driver>[:default].
 #   Defaults to $::os_service_default
 #

spec/acceptance/basic_neutron_spec.rb

@@ -73,7 +73,9 @@ describe 'basic neutron' do
         mechanism_drivers    => ['openvswitch', 'sriovnicswitch']
       }
       class { '::neutron::agents::ml2::sriov': }
-      class { '::neutron::services::lbaas': }
+      class { '::neutron::services::lbaas':
+        service_providers => 'LOADBALANCER:Haproxy:neutron_lbaas.services.loadbalancer.drivers.haproxy.plugin_driver.HaproxyOnHostPluginDriver:default',
+      }
       EOS