executor: don't duplicate FD array to avoid double closing

Just use ExecParam directly, as these are all internal to sd-exec now
anyway. Avoids double close when execution fails after FDs are set up
for inheritance and were already re-arranged.

Fixes https://github.com/systemd/systemd/issues/30412

test/units/testsuite-07.issue-30412.sh

@@ -0,0 +1,31 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: LGPL-2.1-or-later
+set -eux
+set -o pipefail
+
+# Check that socket FDs are not double closed on error: https://github.com/systemd/systemd/issues/30412
+
+mkdir -p /run/systemd/system
+
+rm -f /tmp/badbin
+touch /tmp/badbin
+chmod 744 /tmp/badbin
+
+cat >/run/systemd/system/badbin_assert.service <<EOF
+[Service]
+ExecStart=/tmp/badbin
+Restart=never
+EOF
+
+cat >/run/systemd/system/badbin_assert.socket <<EOF
+[Socket]
+ListenStream=@badbin_assert.socket
+EOF
+
+systemctl daemon-reload
+systemctl start badbin_assert.socket
+
+socat - ABSTRACT-CONNECT:badbin_assert.socket
+
+timeout 10 sh -c 'while systemctl is-active badbin_assert.service; do sleep .5; done'
+[[ "$(systemctl show -P ExecMainStatus badbin_assert.service)" == 203 ]]