r8896: Handle more complex case where field being changed doesn't appear

r8896: Handle more complex case where field being changed doesn't appear
alone in any of userinfo levels. What's needed is extra query step
to fill the userinfo structure and then modify a single field.
The other way to do it is userinfo level 21 with bitmap flags set,
but first all field flags need to be found.

rafal
(This used to be commit 59769977e8ebc54be7fa80f19638b634f52df515)