Remove duplicate NullHandler test fixture

This removes the unused duplicate NullHandler test fixture from the
top-level test module. The other NullHandler in the fixtures module is
used by the StandardLogging fixture in the same module.

Change-Id: I76279ff445860fd78bdd5e074efc77650cd5d071

nova/test.py

@@ -28,7 +28,6 @@ eventlet.monkey_patch(os=False)
 
 import copy
 import inspect
-import logging as std_logging
 import mock
 import os
 
@@ -106,23 +105,6 @@ class TestingException(Exception):
     pass
 
 
-class NullHandler(std_logging.Handler):
-    """custom default NullHandler to attempt to format the record.
-
-    Used in conjunction with
-    log_fixture.get_logging_handle_error_fixture to detect formatting errors in
-    debug level logs without saving the logs.
-    """
-    def handle(self, record):
-        self.format(record)
-
-    def emit(self, record):
-        pass
-
-    def createLock(self):
-        self.lock = None
-
-
 class skipIf(object):
     def __init__(self, condition, reason):
         self.condition = condition