legacy system test fails with "ns1 sent 10 queries to ns7, expected less than 10"

The legacy system test fails on FreeBSD 12.4 on main.

The test fails intermittently in about 1 in 5 cases.

I:legacy:checking recursive lookup to edns 512 + no tcp server does not cause query loops (19)
I:legacy:ns1 sent 10 queries to ns7, expected less than 10
I:legacy:failed

The test has been added in !2500 (merged).

legacy-n1: named.run

legacy-ns7: named.run