Add 'host' to container db filters

This feild is required by method 'list_by_host' in container object.

Change-Id: I8265f7b638deb545c6431afffeac88521713b2cb

zun/db/sqlalchemy/api.py

@@ -132,7 +132,7 @@ class Connection(object):
             filters = {}
 
         filter_names = ['name', 'image', 'project_id', 'user_id',
-                        'memory']
+                        'memory', 'host']
         for name in filter_names:
             if name in filters:
                 query = query.filter_by(**{name: filters[name]})