Fixed problem that file handle (copy of STDOUT and STDERR) is initialized at an unintended timing.

1. Modified as to reset only when 'reset_outputs' method is called explicitly.

Since the mode of binmode which made an after-user-makes change
to the timing which user do not mean will be overwritten.

2. Modified so as not to share the file handle between objects.

Since the time of the subtest to make the object of 'Test::Builder::Formatter::TAP',
file handle of 'Test::Builder::Formatter::TAP' of parent is overwritten.