Deprecate OpenContrail support

The current OpenContrail neutron plugin, which is available in
GitHub[1] is not compatible with the recent OpenStack releases, mainly
because of openstacksdk pinned to <2.

Because the plugin can't be used with recent releases of OpenStack, we
do not expect any users using it as their network backend in their
OpenStack deployment.

[1] https://github.com/tungstenfabric/tf-neutron-plugin

Change-Id: I66cec47a9238dab68445838e5599bfe1c45d2e4e

ceilometer/network/statistics/opencontrail/driver.py

@@ -13,6 +13,7 @@
 # under the License.
 
 import re
+import warnings
 
 from urllib import parse as urlparse
 
@@ -57,6 +58,11 @@ class OpencontrailDriver(driver.Driver):
       opencontrail://localhost:8081/?resource=fip_stats_list&
       virtual_network=default-domain:openstack:public
     """
+    def __init__(self, conf):
+        warnings.warn('Support for OpenContrail is deprecated.',
+                      category=DeprecationWarning, stacklevel=3)
+        super(OpencontrailDriver, self).__init__(conf)
+
     def _prepare_cache(self, endpoint, params, cache):
 
         if 'network.statistics.opencontrail' in cache:

releasenotes/notes/deprecate-contrail-256177299deb6926.yaml

@@ -0,0 +1,5 @@
+---
+deprecations:
+  - |
+    Support for OpenContrail, which is currently known as  Tungsten Fabric, has
+    been deprecated and will be removed in a future release.