Disable atomic file updates on Windows

Utilizing atomic file updates (via Chef, e.g. templates) means needing
Administrator permissions to read the SACL from files. While we expect
chef-client to be run as Administrator or with equivlanet permissions, we
expect chef-dk (chef) to be run as a regular user. Even when logged in as
an Administrator, you need to be running your shell with elevated
privileges for atomic file updates to work.

Fixes #109.
Ensure file_staging_uses_destdir is true

This way we are likely to inherit file ACLs on Windows when we create the
tempfile, since we're avoiding the code that reads and sets the ACLs on
a file move from file_atomic_update.

Chef 12 defaults to file_staging_uses_destdir being true, but prior releases
did not. This ensures we keep this setting.
Merge pull request #134 from opscode/btm/windows-atomic-updates

Disable atomic file updates on Windows