quic: temporarily disable preferred address tests

The way the preferred address mechanism is supposed to work is this: A server might be exposed via multiple network interfaces / addresses. The preferred address is the one that clients should use. If a client uses one of the non-preferred addresses to initially connect to the server, the server will include the preferred address in it's initial transport params back to the client over the original connection. The client then can make a choice: it can either choose to ignore the advertised preferred address and continue using the original, or it can transition the in-flight connection to the preferred address without having to restart the connection. In the latter case, the connection will start making use of the preferred address but it might not do so immediately.

To test this mechanism properly, we should have our server configured on multiple endpoints with one of those marked as the preferred. The connection should start on one and preceed uninterrupted to completion. If the preferred address policy is "accept", the client will accept and transition to the servers preferred address transparently, without interupting the flow.

The current test is deficient because the server is only listening on a single address which is also advertised as the preferred. While the client should get the advertisement, we're not actually making use of the preferred address advertisement and nothing on the connection changes

The ipv6 version of the test is also hanging on some platforms and it's not entirely clear why yet.

/cc @nodejs/quic

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines