Add Additional tests to WindowsFileDelegateTest

This adds tests for WindowsFileDelegate.getDfsShareAclView()
and WindowsFileDelegate.getDfsUncActiveStorageUnc() using
JNA fakes to simulate the Netapi32Ex DFS calls.

This brings the WindowsFileDelegate up to 88% coverage and the
adaptor as a whole to 93% line coverage and 88% branch coverage.

Code Review: http://codereview.appspot.com/90470043