DeploySingleServerGroupTestCase regularly fails on Windows

See http://brontes.lab.eng.brq.redhat.com/viewLog.html?buildId=15206&tab=buildResultsDiv&buildTypeId=WF_MasterIgnoreWindows for an example – this fails repeatedly in the windows runs.

The @After method in the test asserts that the deployment file the test creates is successfully deleted. That may just be a bogus/unnecessary assertion, but rather than just removing it I thought it was better to check a bit first whether the CLI process is holding the file open. It shouldn't need to once upload of the deployment to the server is complete.