Fix upgrading from pre-1.7 databases.
Review Request #5756 — Created April 30, 2014 and submitted
rb-site does a check to see if a dedup operation should be run. This
ends up checking some modern fields that didn't exist pre-1.7.
We now wrap this and catch the exception, handling the case where the
operation fails due to a database error. The assumption we make is that
if there's a database error, we're likely upgrading from a database that
doesn't have these columns, and a dedup is probably needed.
Ran an upgrade on a 1.5.x DB, and a 1.6.x DB. Both upgraded. Before this
change, they both gave errors about a missing column.