Enable horizon plugins by default in docker

Horizon's docker image needs explicit configuration for Kolla to
enable its plugins.

This patch only enables the plugins that actually are installed.

Change-Id: I99a20abc3ac4452a3b10167e615957911327cfaa
Closes-bug: #1723929
(cherry picked from commit 7204290f3c)

docker/services/horizon.yaml

@@ -150,6 +150,28 @@ outputs:
                       - ''
             environment:
               - KOLLA_CONFIG_STRATEGY=COPY_ALWAYS
+              # Installed plugins:
+              - ENABLE_CLOUDKITTY=yes
+              - ENABLE_FWAAS=yes
+              - ENABLE_IRONIC=yes
+              - ENABLE_MAGNUM=yes
+              - ENABLE_MANILA=yes
+              - ENABLE_MURANO=yes
+              - ENABLE_MISTRAL=yes
+              - ENABLE_NEUTRON_LBAAS=yes
+              - ENABLE_SAHARA=yes
+              - ENABLE_TROVE=yes
+              # Not installed:
+              - ENABLE_FREEZER=no
+              - ENABLE_KARBOR=no
+              - ENABLE_DESIGNATE=no
+              - ENABLE_SEARCHLIGHT=no
+              - ENABLE_SENLIN=no
+              - ENABLE_SOLUM=no
+              - ENABLE_TACKER=no
+              - ENABLE_WATCHER=no
+              - ENABLE_ZAQAR=no
+              - ENABLE_ZUN=no
       host_prep_tasks:
         - name: create persistent logs directory
           file: