Using v2 as the default version of Glance

Glance API v1 has been deprecated, so it's better to use v2 as
the default API version in openstackclient.

Closes-Bug: 1642772

Change-Id: I7d9e3228a2f3a3d0da437b7ee6f23e528de27fd3

Author: openstacker

openstackclient/image/client.py

@@ -22,7 +22,7 @@
 
 LOG = logging.getLogger(__name__)
 
-DEFAULT_API_VERSION = '1'
+DEFAULT_API_VERSION = '2'
 API_VERSION_OPTION = 'os_image_api_version'
 API_NAME = "image"
 API_VERSIONS = {

releasenotes/notes/bug-1642772-19f53765bef8ee91.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - Changed the default version of ``OS_IMAGE_API_VERSION`` to ``2``. Image v1
+    has been deprecated for more than six months and other projects, such as
+    `shade` and `os-client-config` are using Image v2 by default as well.
+    [Bug `1642772 <https://bugs.launchpad.net/bugs/1642772>`_]