BC break after patch

[Mark Scherer]

#198 broke BC on some parts

See 5af4766

var_dump(\Cake\Chronos\Chronos::parse('8:00:00')->toTimeString());
var_dump(\Cake\Chronos\Chronos::parse('8:00:00', 'Etc/UTC')->toTimeString());
var_dump(\Cake\Chronos\Chronos::parse('08:00:00')->toTimeString());
var_dump(\Cake\Chronos\Chronos::parse('08:00:00', 'Etc/UTC')->toTimeString());