Add collectd-gnocchi plugin

in order to be able to use gnocchi as data store for collectd metrics.

Change-Id: Iad404c2c888d2b3b8aed6497224e59f5049ba427

docker/collectd/Dockerfile.j2

@@ -17,7 +17,8 @@ LABEL maintainer="{{ maintainer }}" name="{{ image_name }}" build-date="{{ build
       'collectd-ceph',
       'collectd-disk',
       'collectd-python',
-      'collectd-virt'
+      'collectd-virt',
+      'python-collectd-gnocchi'
   ] %}
 
   {% if base_arch =='x86_64' %}