osd: rewind_divergent_log needs to dirty log if crt changes or ...

osd: rewind_divergent_log needs to dirty log if crt changes or ...
rollback_info_trimmed_to changes

PGLog::rewind_divergent_log was only causing the log to be marked
dirty and checkpointed if there were divergent entries. However
after a PG split it is possible that the log can be rewound
modifying crt and/or rollback_info_trimmed_to without creating
divergent entries because the entries being rolled back were
all split into the other PG.

Failing to checkpoint the log generates a window where if the OSD
is reset you can end up with crt (and rollback_info_trimmed_to) > head.
One consequence of this is asserts like
ceph_assert(rollback_info_trimmed_to == head); firing.

Fixes: https://tracker.ceph.com/issues/55141
Signed-off-by: Bill Scales <bill_scales@uk.ibm.com>
(cherry picked from commit d8f78adf85f8cb11deeae3683a28db92046779b5)