CONNECT engine table_type=JDBC should not require FILE priv

For security reasons it would be great if we did not have to grant FILE permission to everyone who uses a CONNECT JDBC table. Currently we have to grant FILE to all users, even non-administrators, which increases the chance of data being leaked by accident. We do use secure_file_priv to help this, but ideally no user would need FILE priv, or if that isn't possible for some reason, at least not require FILE to use a connect JDBC table.