TEST-45-TIMEDATE: rotate journal before parsing log message

TEST-45-TIMEDATE: rotate journal before parsing log message

Similar to 04ade57a4233750f45fbc5fa2b5f52adfb435de5.

Fixes the following failure (long line is wrapped):
```
TEST-45-TIMEDATE.sh[234]: + journalctl --sync
TEST-45-TIMEDATE.sh[234]: + for _ in {0..9}
TEST-45-TIMEDATE.sh[234]: + journalctl -q -n 1 '--since=2025-09-01 17:09:25.442936' -p info -t busctl --grep .
TEST-45-TIMEDATE.sh[363]: Sep 01 17:09:25 H busctl[351]: {"type":"signal","endian":"l","flags":1,"version":1,
  "cookie":67,"timestamp-realtime":1756746565578529,"sender":":1.11","path":"/org/freedesktop/timedate1",
  "interface":"org.freedesktop.DBus.Properties","member":"PropertiesChanged","payload":{"type":"sa{sv}as",
    "data":["org.freedesktop.timedate1",{"NTP":{"type":"b","data":false}},[]]}}
TEST-45-TIMEDATE.sh[366]: ++ journalctl -q -n 1 '--since=2025-09-01 17:09:25.442936' -p info -t busctl -o cat
TEST-45-TIMEDATE.sh[367]: ++ jq -r '.payload.data[1].NTP.data'
TEST-45-TIMEDATE.sh[366]: Journal file /run/log/journal/07946b7846564ac0ad1c86e8cabed329/system.journal is truncated, ignoring file.
TEST-45-TIMEDATE.sh[234]: + [[ '' == \f\a\l\s\e ]]
```