Race condition causes unit test to occasionally fail

Occasionally, I get the following unit test failure:

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FAIL: test_run_instances (nova.tests.test_direct.DirectCloudTestCase)
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Traceback (most recent call last):
  File "/Users/lorin/nova/trunk/nova/tests/test_cloud.py", line 469, in test_run_instances
    self.assertEqual(instance['instanceState']['name'], 'networking')
AssertionError: u'scheduling' != 'networking'

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The issue seems to be that the test assumes that the rpc.cast in nova.compute.api:create completes on time, and sometimes it doesn't.

The test code (test_cloud.py) already has the following code to reduce the probability of this happening:

        rpc_cast = rpc.cast

        def finish_cast(*args, **kwargs):
            rpc_cast(*args, **kwargs)
            greenthread.sleep(0.2)

        self.stubs.Set(rpc, 'cast', finish_cast)

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If you comment out the sleep statement, the bug can be reliably reproduced.