Clarify error messages and comments

Change-Id: I0016b323de4c41fa2face877852b056f8eb562f2
diff --git a/util.py b/util.py
index 8c47318..c2dc725 100644
--- a/util.py
+++ b/util.py
@@ -86,7 +86,7 @@
             elif command == 'db.get_vlan_name_by_id':
                 ret = db.get_vlan_name_by_id(data['vlan_id'])
             else:
-                raise InputError("Unknown query command \"%s\"" % command)
+                raise InputError("Unknown db_query command \"%s\"" % command)
 
         except InputError:
             raise
@@ -112,7 +112,7 @@
             elif command == 'daemon.statistics':
                 ret['uptime'] = time.time() - state.starttime
             else:
-                raise InputError("Unknown query command \"%s\"" % command)
+                raise InputError("Unknown daemon_query command \"%s\"" % command)
 
         except InputError:
             raise
@@ -122,7 +122,7 @@
 
         return ret
 
-    # Helper wrapper for API functions modifying database state
+    # Helper wrapper for API functions modifying database state only
     def perform_db_update(self, state, command, data):
         print 'perform_db_update'
         print command