Tests fail if /dev/log does not exist.

[Chuck Short]

While building in a local builder for an debian package, the unit tests will fail if /dev/log does not exist.

======================================================================
FAIL: os_xenapi.tests.plugins.test_dom0_pluginlib.PluginlibDom0.test_configure_logging
os_xenapi.tests.plugins.test_dom0_pluginlib.PluginlibDom0.test_configure_logging
----------------------------------------------------------------------
_StringException: Empty attachments:
  stderr
  stdout

Traceback (most recent call last):
  File "os_xenapi/tests/plugins/test_dom0_pluginlib.py", line 42, in test_configure_logging
    self.dom0_pluginlib.configure_logging(name)
  File "/<<PKGBUILDDIR>>/os_xenapi/dom0/etc/xapi.d/plugins/dom0_pluginlib.py", line 37, in configure_logging
    sysh = logging.handlers.SysLogHandler('/dev/log')
  File "/usr/lib/python2.7/logging/handlers.py", line 761, in __init__
    self._connect_unixsocket(address)
  File "/usr/lib/python2.7/logging/handlers.py", line 789, in _connect_unixsocket
    self.socket.connect(address)
  File "/usr/lib/python2.7/socket.py", line 228, in meth
    return getattr(self._sock,name)(*args)
socket.error: [Errno 2] No such file or directory