Fix intermittent test failures

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Classifier IP6 UDP proto Test Case

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connect: No such file or directory

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ERROR: setUpClass (test_ip4.TestIPLoadBalance)

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Traceback (most recent call last):

  File "/vpp/test/framework.py", line 424, in setUpClass

    cls.statistics = VPPStats(socketname=cls.stats_sock)

  File "build/bdist.linux-x86_64/egg/vpp_papi/vpp_stats.py", line 120, in _init_

    raise IOError()

IOError