Use correct version string

Rather than using pbr's version_string (that returns the short version)
we should use the release_verison that includes the full version,
including any VCS status.

Author: alvarolopez

caso/__init__.py

@@ -18,6 +18,6 @@
 
 
 __version__ = pbr.version.VersionInfo(
-    'caso').version_string()
+    'caso').release_string()
 
 user_agent = "caso/%s (OpenStack)" % __version__