TEST-87-AUX-UTILS-VM: make coredumps stored in archived journal file

TEST-87-AUX-UTILS-VM: make coredumps stored in archived journal file

Fixes the following race:
```
TEST-87-AUX-UTILS-VM.sh[839]: + coredumpctl -1
TEST-87-AUX-UTILS-VM.sh[1169]: TIME                        PID UID GID SIG     COREFILE EXE             SIZE
TEST-87-AUX-UTILS-VM.sh[1169]: Sun 2025-07-27 23:22:02 UTC 885   0   0 SIGABRT present  /tmp/test-dump 19.9K
TEST-87-AUX-UTILS-VM.sh[839]: + coredumpctl -n 1
TEST-87-AUX-UTILS-VM.sh[1172]: Journal file /var/log/journal/a8285330872602d1377cbaaf68869946/system.journal is truncated, ignoring file.
TEST-87-AUX-UTILS-VM.sh[1172]: No coredumps found.
```