test: rotate journal before storing coredumps

test: rotate journal before storing coredumps

Hopefully fixes the failure like
https://jenkins-systemd.apps.ocp.cloud.ci.centos.org/job/upstream-vagrant-archlinux-sanitizers/2558/
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[   66.708894] testsuite-74.sh[728]: + coredumpctl --json=off
[   66.709344] testsuite-74.sh[826]: TIME                        PID UID GID SIG     COREFILE EXE             SIZE
[   66.709773] testsuite-74.sh[826]: Tue 2023-05-23 22:10:17 UTC 739   0   0 SIGTRAP journal  /tmp/test-dump     -
[   66.711134] testsuite-74.sh[826]: Tue 2023-05-23 22:10:18 UTC 747   0   0 SIGABRT journal  /tmp/test-dump     -
[   66.711789] testsuite-74.sh[826]: Tue 2023-05-23 22:10:19 UTC 763   0   0 SIGTRAP present  /tmp/test-dump 53.5K
[   66.712460] testsuite-74.sh[826]: Tue 2023-05-23 22:10:20 UTC 776   0   0 SIGABRT present  /tmp/test-dump 53.3K
[   66.713505] testsuite-74.sh[728]: + coredumpctl --root=/
[   66.714144] testsuite-74.sh[828]: TIME                        PID UID GID SIG     COREFILE EXE             SIZE
[   66.714535] testsuite-74.sh[828]: Tue 2023-05-23 22:10:17 UTC 739   0   0 SIGTRAP journal  /tmp/test-dump     -
[   66.715208] testsuite-74.sh[828]: Tue 2023-05-23 22:10:18 UTC 747   0   0 SIGABRT journal  /tmp/test-dump     -
[   66.715907] testsuite-74.sh[828]: Tue 2023-05-23 22:10:19 UTC 763   0   0 SIGTRAP present  /tmp/test-dump 53.5K
[   66.716565] testsuite-74.sh[828]: Tue 2023-05-23 22:10:20 UTC 776   0   0 SIGABRT present  /tmp/test-dump 53.3K
[   66.717494] testsuite-74.sh[728]: + coredumpctl --directory=/var/log/journal
[   66.718188] testsuite-74.sh[830]: TIME                        PID UID GID SIG     COREFILE EXE             SIZE
[   66.882072] testsuite-74.sh[830]: Tue 2023-05-23 22:10:17 UTC 739   0   0 SIGTRAP journal  /tmp/test-dump     -
[   66.882642] testsuite-74.sh[830]: Tue 2023-05-23 22:10:18 UTC 747   0   0 SIGABRT journal  /tmp/test-dump     -
[   66.883450] testsuite-74.sh[830]: Tue 2023-05-23 22:10:19 UTC 763   0   0 SIGTRAP present  /tmp/test-dump 53.5K
[   66.883944] testsuite-74.sh[830]: Tue 2023-05-23 22:10:20 UTC 776   0   0 SIGABRT present  /tmp/test-dump 53.3K
[   66.885448] testsuite-74.sh[728]: + coredumpctl --file=/var/log/journal/2e1ed84be19a4e22adfc99ad849be1f6/system.journal
[   66.885989] testsuite-74.sh[728]: + at_exit
[   66.894162] coredumpctl[833]: No coredumps found.
---