disassociate rdatasets when cleaning up [v9_16]
requested to merge 3447-lib-dns-tkey-c-free_namelist-should-be-disassociating-associated-rdatatsets-v9_16 into v9_16
free_namelist could be passed names with associated rdatasets when handling errors. These need to be disassociated before calling dns_message_puttemprdataset.
(cherry picked from commit 745d5edc)
Closes #3447 (closed)
Edited by Mark Andrews