core: Propagate condition failed state to triggering units.

Alternative to https://github.com/systemd/systemd/pull/20531.

Whenever a service triggered by another unit fails condition checks,
stop the triggering unit to prevent systemd busy looping trying to
start the triggered unit.

test/testsuite-63.units/test63.service

@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: LGPL-2.1-or-later
 [Unit]
-ConditionPathExists=!/tmp/nonexistent
+ConditionPathExists=/tmp/nonexistent
 
 [Service]
 ExecStart=true

test/units/testsuite-10.service

@@ -13,5 +13,5 @@ ExecStart=-socat -T20 OPEN:test.file UNIX-CONNECT:/run/test.ctl
 # systemd enough time even on slower machines, to reach the trigger limit.
 ExecStart=sleep 10
 ExecStart=sh -x -c 'test "$(systemctl show test10.socket -P ActiveState)" = failed'
-ExecStart=sh -x -c 'test "$(systemctl show test10.socket -P Result)" = trigger-limit-hit'
+ExecStart=sh -x -c 'test "$(systemctl show test10.socket -P Result)" = service-condition-failed'
 ExecStart=sh -x -c 'echo OK >/testok'

test/units/testsuite-63.service

@@ -8,10 +8,10 @@ Type=oneshot
 ExecStart=rm -f /tmp/nonexistent
 ExecStart=systemctl start test63.path
 ExecStart=touch /tmp/test63
-# Make sure systemd has sufficient time to hit the start limit for test63.service.
 ExecStart=sleep 2
-ExecStart=sh -x -c 'test "$(systemctl show test63.service -P ActiveState)" = failed'
-ExecStart=sh -x -c 'test "$(systemctl show test63.service -P Result)" = start-limit-hit'
+# Ensure both the service and the corresponding path unit go inactive due to the failed condition check.
+ExecStart=sh -x -c 'test "$(systemctl show test63.service -P ActiveState)" = inactive'
+ExecStart=sh -x -c 'test "$(systemctl show test63.service -P Result)" = success'
 ExecStart=sh -x -c 'test "$(systemctl show test63.path -P ActiveState)" = failed'
-ExecStart=sh -x -c 'test "$(systemctl show test63.path -P Result)" = unit-start-limit-hit'
+ExecStart=sh -x -c 'test "$(systemctl show test63.path -P Result)" = unit-condition-failed'
 ExecStart=sh -x -c 'echo OK >/testok'