[9.18] fix: test: Disable keyfromlabel collision avoidance in tests

With the collision avoidance on, some of the tests would occasionally
fail. None of the tests using keyfromlabel are revoking the keys so it
should be safe to disable it.

Closes #5554

Backport of MR !11066

Merge branch 'backport-5554-disable-keyfromlabel-collision-avoidance-in-tests-9.18' into 'bind-9.18'

See merge request isc-projects/bind9!11075