CORD-1550: Make driver and client compatible with keystone v3 system

Add a version property to keystone client and did some modification
so that the v3 and v2 have the same programming interface.

Change-Id: I26e2f6d91e5f5d09409a9a71504318e787819023
diff --git a/xos/synchronizer/client.py b/xos/synchronizer/client.py
index 817f184..b64e86f 100644
--- a/xos/synchronizer/client.py
+++ b/xos/synchronizer/client.py
@@ -117,6 +117,9 @@
 
     @require_enabled
     def __getattr__(self, name):
+        if 'version' == name:
+            version = self.url.rpartition('/')[2]
+            return 'v2.0' if 'v2.0' == version else 'v3.0'
         return getattr(self.client, name)