Sometimes 'named' doesn't exit quickly on shutdown

Summary

Sometimes 'named' doesn't exit quickly on shutdown

BIND version used

This behavior has been seen in BIND 9.16 but not BIND 9.11

Steps to reproduce

Detail on RT tickets #20232 and #20231

What is the current bug behavior?

BIND can wait up to 10 sec or the value of "resolver-query-timeout" before exiting

What is the expected correct behavior?

BIND should exit gracefully but not wait for outstanding queries to time out

RT #20232