Change the default storage backend to v2/influxdb

This updates the default storage backend from v1/sqlalchemy to v2/influxb.

Work items:

* Update default storage interface version from 1 to 2

* Update default storage backend from sqlalchemy to influxdb

Depends-On: https://review.openstack.org/#/c/609986/
Change-Id: Icf3854f92b89be20077bbe7b9aac5ea13e3f9052
Story: 2001372
Task: 26825

cloudkitty/storage/__init__.py

@@ -25,11 +25,11 @@ LOG = logging.getLogger(__name__)
 
 storage_opts = [
     cfg.StrOpt('backend',
-               default='sqlalchemy',
+               default='influxdb',
                help='Name of the storage backend driver.'),
     cfg.IntOpt('version',
                min=1, max=2,
-               default=1,
+               default=2,
                help='Storage version to use.'),
 ]
 

releasenotes/notes/default-to-v2-storage-a5ecac7e73dafa6d.yaml

@@ -0,0 +1,11 @@
+---
+upgrade:
+  - |
+    CloudKitty's storage interface defaults to v2 from now on. v1 will be
+    deprecated in a future release. Documentation about how to upgrade the
+    storage backend along with some tools will be available at that point. New
+    deployments should use the v2 storage interface.
+
+    The default v2 backend is ``influxdb``. In order to keep using
+    ``sqlalchemy``, specify "version = 1" and "backend = sqlalchemy" in the
+    ``[storage]`` section of the configuration.