Change grafana plugin install logic

Changing the way in which we specify grafana plugins to install. This is
due to a change upstream which now allows plugins to be installed in an
additive method instead of replacing the upstream default plugins [1].

[1] https://review.opendev.org/c/openstack/kolla/+/913184

Co-authored-by: Will Szumski <[email protected]>

Author: technowhizz

etc/kayobe/kolla.yml

@@ -337,11 +337,6 @@ kolla_build_blocks:
   bifrost_base_header: |
     ADD additions-archive /
     ENV TOX_CONSTRAINTS_FILE=/requirements/upper-constraints.txt
-  grafana_plugins_install: |
-    RUN grafana-cli plugins install vonage-status-panel \
-        && grafana-cli plugins install grafana-piechart-panel \
-        && grafana-cli plugins install grafana-opensearch-datasource \
-        && grafana-cli plugins install gnocchixyz-gnocchi-datasource
   ironic_inspector_header: |
     ADD additions-archive /
   magnum_base_footer: |
@@ -360,6 +355,9 @@ kolla_build_blocks:
 kolla_build_customizations_common:
   bifrost_base_pip_packages_append:
     - /additions/*
+  grafana_plugins_append:
+    - grafana-piechart-panel
+    - vonage-status-panel
   ironic_inspector_pip_packages_append:
     - /additions/*
   neutron_server_packages_append: