Fix prepare_release make target
Fix prepare_release make target

The previous version did not fetch unlocked deps. Even though
USE_REBAR_LOCKED was removed, the Make instance had already started,
found USE_REBAR_LOCKED, and set the config file to use. With this
approach, we simply call get-deps using the default unlocked config
during the prepare_release execution via the new unlocked_deps target.

chef/erchef,chef/erchef