Migrate to nova api version 2.1

The Nova v2 API code has been completely removed from Nova by
change[1]. Although Nova still supports v2 compatible API with the
legacy endpoint, it is better to switch to use Nova v2.1 in Heat.

This change sets version='2.1' when init novaclient
instance, then we can use novaclient v2 and will
use nova api v2.1.

[1] https://review.openstack.org/#/c/311653/

Change-Id: I428abb4ca05847da8ffc2da7157aa5c34263a205
Closes-Bug: #1588155
Partial-Bug: #1588171
diff --git a/common/clients.py b/common/clients.py
index 7a674bf..e7a3f31 100644
--- a/common/clients.py
+++ b/common/clients.py
@@ -64,7 +64,7 @@
 
     CINDERCLIENT_VERSION = '2'
     HEATCLIENT_VERSION = '1'
-    NOVACLIENT_VERSION = '2'
+    NOVA_API_VERSION = '2.1'
     CEILOMETER_VERSION = '2'
 
     def __init__(self, conf):
@@ -142,7 +142,7 @@
 
         # Create our default Nova client to use in testing
         return nova_client.Client(
-            self.NOVACLIENT_VERSION,
+            self.NOVA_API_VERSION,
             *client_args,
             service_type='compute',
             endpoint_type='publicURL',