remove uneeded Hyperctl::Sysfs#refresh calls in unit tests
add Hyperctl::Sysfs#cores
add Hyperctl::Sysfs#all_cores_enabled?
add Hyperctl::Sysfs#sibling_cores
add Hyperctl::Sysfs#all_siblings_disabled?
refactor Hyperctl::disable

Replace method guts with Hyperctl::Sysfs#sibling_cores
add --status flag to hyperctl script