[1372] fixed docstring to match the implementation. the previous one

was a naive copy of a similar fake method used in a different test.

src/bin/xfrout/tests/xfrout_test.py.in

@@ -98,8 +98,8 @@ class MockDataSrcClient:
         '''Mock version of find_zone().
 
         It returns itself (subsequently acting as a mock ZoneFinder) for
-        some test zone names.  For some others it returns either NOTFOUND
-        or PARTIALMATCH.
+        some test zone names.  For a special name it returns NOTFOUND to
+        emulate the condition where the specified zone doen't exist.
 
         '''
         self._zone_name = zone_name