Adding api_version to FakeAPP

In order to use the app.api_version dict we need to add to the FakeApp
as well so we can test it.

Patch that will benefit from this: https://review.openstack.org/#/c/572536/

Change-Id: Ifd0f1e8cafb8b9296eb8d96648b3c5f3f1b63ddf

osc_lib/tests/fakes.py

@@ -105,6 +105,7 @@ class FakeApp(object):
     def __init__(self, _stdout, _log):
         self.stdout = _stdout
         self.client_manager = None
+        self.api_version = {}
         self.stdin = sys.stdin
         self.stdout = _stdout or sys.stdout
         self.stderr = sys.stderr