Change exit_checker comment on returned status

    # exit_checker is used by run() directly after completion of a command.

    # it receives the exit code from that command and is expected to return

    # 1 (for success) or 0 (for failure).  This is the value that will be

    # returned by run().

    # NOTE: When run() gets the option 'capture => 1', this hook is ignored.

    # 1 (for success) or 0 (for failure).  This is the status value that run()

    # will give back (through the |statusvar| referens and as returned value

    # when capture => 1 doesn't apply).

    exit_checker => sub { return shift == 0 ? 1 : 0 },

    );