fix host resource repr to use 'host' attribute

This change fixes an AttributeError raised when attempting to
represent a host resource as a string.

Change-Id: I33369b20ed7f5219c3b507107b8f3a37b46eacee
Closes-Bug: #1327005

novaclient/tests/v1_1/test_hosts.py

@@ -78,3 +78,7 @@ def test_host_shutdown(self):
         host.shutdown()
         self.assert_called(
             'GET', '/os-hosts/sample_host/shutdown')
+
+    def test_hosts_repr(self):
+        hs = self.cs.hosts.get('host')
+        self.assertEqual('<Host: dummy>', repr(hs[0]))

novaclient/v1_1/hosts.py

@@ -21,7 +21,7 @@
 
 class Host(base.Resource):
     def __repr__(self):
-        return "<Host: %s>" % self.host_name
+        return "<Host: %s>" % self.host
 
     def _add_details(self, info):
         dico = 'resource' in info and info['resource'] or info