maint: Fix build break due to recent merge from 2.7.x to master

The resource_spec was failing because /etc is not considered a
fully-qualified path on Windows. Using File.expand_path fixes that.

The suidmanager_spec was failing because we weren't stubbing the
microsoft_windows feature, so SUIDManager.asuser was a no-op when
running as root, and our expectations weren't being met.
(cherry picked from commit af87f32a016a5ed48353f516f9558f95c54c50b4)