Comment 2 for bug 1552861

Tested and signed off, with an addition: user/gmcharlt/lp1552861_signoff

During testing, I noted that if that setting was set to an invalid value, it broke the library settings editor. Consequently, the add-on patch arranges during the database update to report, then remove, any instances of the vandelay.default_match_set setting that don't correspond to a vms row.