Revert "test: Run end.sh when running integration tests with mkosi"

It seems this introduced a regression in the CentOS CI;

14:25:58 FAILED TASKS:14:25:58 -------------
14:25:58 TEST-03-JOBS
14:25:58 TEST-52-HONORFIRSTSHUTDOWN
14:25:58 TEST-63-PATH

Revert for now.

This reverts commit da3c6fc553.

test/integration-test-wrapper.py

@@ -71,7 +71,6 @@ def main():
 
         [Service]
         StandardOutput=journal+console
-        ExecStart=/usr/lib/systemd/tests/testdata/units/end.sh
         """
     )
 

test/units/end.service

@@ -3,7 +3,6 @@
 Description=End the test
 After=testsuite.target
 OnFailure=poweroff.target
-OnSuccess=poweroff.target
 OnFailureJobMode=replace-irreversibly
 
 [Service]

test/units/end.sh

@@ -13,4 +13,5 @@ set -o pipefail
 (! journalctl -q -o short-monotonic --grep "[F]ailed to parse serialized line" >>/failed)
 (! journalctl -q -o short-monotonic --grep "[F]ailed to (de)?serialize \w+" >>/failed)
 
+systemctl poweroff --no-block
 exit 0