[9.20] fix: usr: Fix potential resource during resolver error handling

Under specific error conditions during query processing, resources were not
being properly released, which could eventually lead to unnecessary memory
consumption for the server.  The a potential resource leak in the resolver
has been fixed.

Backport of MR !11658

Merge branch 'backport-ondrej/fix-pthread-primitives-usage-9.20' into 'bind-9.20'

See merge request isc-projects/bind9!11706