Bug with && in piped functions in minimal-config bash

[Martijn Dekker]

My development with Modernish just exposed the following bug on bash
4.4.0(1)-maint, bash-20161028 snapshot, compiled with
--enable-minimal-config --enable-alias:

$ fn() { false && echo bug || echo ok; }
$ fn
ok
$ fn
ok
$ fn | cat
ok
$ fn | cat
bug
$ fn | cat
bug
$ (fn) | cat
ok

So apparently this only occurs if the function is piped into another
command, without explicitly declaring it to run in a subshell, and only
from the second time on.

Thanks,

- M.