journal: do not rotate unrelated journal files when full or corrupted

journal: do not rotate unrelated journal files when full or corrupted

When we fail to add an entry to a journal file, typically when the file
is full or corrupted, it is not necessary to rotate other journal files.

Not only that's unnecessary, rotating all journal files allows
unprivileged users to wipe system or other user's journals by writing
many journal entries to their own user journal file.

Let's rotate all journal files only when
- it is really requested by a privileged user (e.g. by journalctl --rotate), or
- the system time jumps backwards.
And, otherwise rotate only the journal file we are currently writing.