daemon: don't bother checking for existing FD flags

daemon: don't bother checking for existing FD flags

FD_CLOEXEC is the only currently defined FD flag, and has been
the case for decades at this point.  I highly doubt any default
FD flag will ever be forced on us by the kernel, init system, or
Perl.  So save ourselves a syscall and just call F_SETFD with
the assumption FD_CLOEXEC is the only FD flag that we'd ever
care for.