Downgrade the dns_clientinfo_t structure to not contain dbversion
_AGE was bumped to 2 and 1 respectively, but the
clientinfomethods->dbversion() method is not used anywhere and instead
clientinfo->dbversion() method is the correct way of accessing the method.
There's also now way how to set the function, so it is always NULL.
We should also probably have a test that
dlz_minimal.h versions are always equal or lower than the clientinfo.h versions, but that could be solved in a separate ticket.
Closes #971 (closed)