[9.20] fix: test: Prevent intermittent setup.sh failures in the "statschannel" system test
requested to merge backport-4781-statschannel-setup-can-fail-due-to-short-validity-interval-9.20 into bind-9.20
Don't verify the just signed zone as the RRSIGs could have expired before the signing process completes
Closes #4781 (closed) #2476 (closed)
Backport of MR !9114 (merged)