internal/testutil: Exclude flakey check.v1 tests from third-party-go-{test,race}
internal/testutil: Exclude flakey check.v1 tests from third-party-go-{test,race}

It was still being flakey in third-party-go-test, although less flakey
than in third-party-go-race.

Change-Id: Ia87eee2334a0a44e5993e0ce5e5e8f45c01542ae

vanadium/go.devtools,vanadium/go.devtools,vanadium/go.devtools