[mysql] needs to `reconnect!` when recreating database (fixes 539)

aligning with https://github.com/rails/rails/commit/2088bf27981137a2c6c8b2f718f33b417b4045af
try resolving config 'database' (if missing) from JDBC url: in rake tasks
even more (rake task) config_from_url resolving for Oracle/MS-SQL