Allow shorter resolver-query-timeout configuration

There are use cases for which shorter timeout values make sense. For example if there is a load balancer which sets RD=1 and forwards queries to a BIND resolver which is then configured to talk to backend servers which are not visible in the public NS set. WIth a shorter timeout value the frontend can give back SERVFAIL early when backends are not available and the ultimate client will not penalize the BIND-frontend for non-response.

Closes #4320