Enhanced offline_db 'stale data' check in weekly backup script.
Add a check to verify that the offline_db is current (based on
the journal counter) before doing the database swap in the
weekly backup script.
This addresses a scenario where a calamity of errors could cause
the offline_db to be stale before the weekly backup script is run.
A safety feature already in the SDP ensures that the offline_db is
not incomplete, e.g. in the process of being written, as could occur
if there were a sudden power off during checkpoint recovery. The
improved check in this job will also verify that the data is current.