DM-42411: Update 8c57494cabcc.py to support offline mode.

[andy-slac]

As this script depends on schema reflection, it needs a workaround for using non-mock connection for reflection.

Checklist

• added documentation for a new migration script

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (1edff52) 54.36% compared to head (d8b3a94) 54.35%.

Files	Patch %	Lines
...ython/lsst/daf/butler_migrate/butler_attributes.py	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #33      +/-   ##
==========================================
- Coverage   54.36%   54.35%   -0.01%     
==========================================
  Files          33       33              
  Lines        1146     1148       +2     
  Branches      255      255              
==========================================
+ Hits          623      624       +1     
- Misses        489      490       +1     
  Partials       34       34              

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[andy-slac]

I am going to merge this branch so that this is not forgotten. Ticket is still open, I'll close it after actual migration happens.