[9.18] chg: test: Be more patient when stopping servers in the system tests
requested to merge backport-ondrej-increase-the-time-to-wait-for-servers-to-gracefully-shutdown-9.18 into bind-9.18
When the TCP test is run on the busy server, the server might take a while to wind the server down because it might still be processing all that 300k invalid XFR requests.
Increate the rncd wait time to 120 seconds, the SIGTERM time to 300 seconds, and reduce the time to wait for ans servers from 1200 second to just 120 seconds.
(cherry picked from commit d9714723)
Backport of MR !6847 (merged)
Edited by Michal Nowak