SIGINT and process substitution leakage

[Grisha Levit]

Running the below a few times results in a stray child bash process
(and a borked terminal, as the child will still read from the same
tty):

    kill -INT -$$ & while :; do : <(:); done

This seems to have started with bash-20150724 [1] and is present in
the current devel branch.

[1] 
https://git.savannah.gnu.org/cgit/bash.git/commit/?h=devel&id=7afeb718cb55ab9f224936a2b58cde07559eb59f