Add python-sqlalchemy-collectd client

sqlalchemy-collectd was added in
I2bcaa44c184bb24e5caeeb8d204dda627de59c91, however it also must
be installed alongside anywhere that python-sqlalchemy is installed
since it provides an in-process plugin that transmits metrics
to a remote collectd daemon.

Also adds the python3 version of the package to the py3 version of
the collecd/Dockerfile.j2.

Note this is currently an *RPM only* package, and as of this
commit is not yet availble for other packaging systems.

Change-Id: If598da717653a383a2d3b3373c56517f8bca832f

docker/collectd/Dockerfile.j2

@@ -49,6 +49,7 @@ LABEL maintainer="{{ maintainer }}" name="{{ image_name }}" build-date="{{ build
       'collectd-ovs_events',
       'collectd-ovs_stats',
       'collectd-snmp_agent',
+      'python3-sqlalchemy-collectd'
   ] %}
   {% else %}
   {% set collectd_packages = collectd_packages + [

docker/openstack-base/Dockerfile.j2

@@ -86,6 +86,7 @@ LABEL maintainer="{{ maintainer }}" name="{{ image_name }}" build-date="{{ build
             'python3-routes',
             'python3-saharaclient',
             'python3-sqlalchemy',
+            'python3-sqlalchemy-collectd',
             'python3-sqlparse',
             'python3-swiftclient',
             'python3-sysv_ipc',
@@ -165,6 +166,7 @@ LABEL maintainer="{{ maintainer }}" name="{{ image_name }}" build-date="{{ build
             'python-routes',
             'python-saharaclient',
             'python2-sqlalchemy',
+            'python2-sqlalchemy-collectd',
             'python-sqlparse',
             'python-swiftclient',
             'python-tooz',