The vault plugin renames vault_profiles to p_vault_profiles, and SQLite
rewrites ssh_data's foreign key to follow it. Uninstalling the plugin then
dropped p_vault_profiles and left ssh_data pointing at a missing table, so
creating, cloning and deleting hosts failed with "no such table:
main.p_vault_profiles". Postgres and MySQL refused the uninstall instead.
The column was already copied into the vault plugin's host settings by 2.9,
so retire it on every engine. The SQLite boot drop also repairs databases
already in the broken state; MySQL drops the column's foreign key first.
