Implement Locker.Locked() for windows
Implement Locker.Locked() for windows

The Locked() method must be implemented so that Save() will work on
windows.

Fixes: c7ba5749d44a ("Add lock sanity checks to Save() methods")
See: https://github.com/containers/storage/pull/210#issuecomment-416671810
Reported-by: Miloslav Trmač <9c008e38982a5397deb855345fb164f0558459ae@redhat.com>
Signed-off-by: Zac Medico <a17fa1dcf5b7e2df0c563c7a30fa1870d6a8ff57@gmail.com>

containers/storage,containers/storage,rhatdan/storage,rhatdan/storage,rhatdan/storage,containers/storage