Adding filter to UserTopicAuth

Change-Id: I3ff383f6f461a22969aa490681d4b4964894d36b
Signed-off-by: Eduardo Sousa <eduardo.sousa@canonical.com>
diff --git a/osm_nbi/admin_topics.py b/osm_nbi/admin_topics.py
index d894a09..9f2eb68 100644
--- a/osm_nbi/admin_topics.py
+++ b/osm_nbi/admin_topics.py
@@ -559,7 +559,10 @@
         :param filter_q: filter of data to be applied
         :return: The list, it can be empty if no one match the filter.
         """
-        return self.auth.get_user_list()
+        if not filter_q:
+            filter_q = {}
+
+        return self.auth.get_user_list(filter_q)
 
     def delete(self, session, _id, dry_run=False):
         """