At the time of commit 6a2a70a02 we didn't use latch infrastructure in
the postmaster. We're planning to start doing that, so we'd better make
sure that the signalfd inherited from a postmaster is not duplicated and
then leaked in the child.
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>
Discussion: https://postgr.es/m/CA%2BhUKG%2BZ-HpOj1JsO9eWUP%2Bar7npSVinsC_npxSy%2BjdOMsx%3DGg%40mail.gmail.com