The tests TestLoopbackLocalAPI, TestLoopbackSOCKS5, and TestTwoDevicePing
were previously marked as flaky globally but had their marks removed after
fixes. However, they appear to still be flaky specifically on macOS.
Re-add flaky marks conditionally for darwin only, allowing the tests to
run normally on Linux and Windows where they pass reliably.
Change-Id: I7b81a16a12437c9aa55f2c9e9fde08d39499cabe
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Avery Pennarun <apenwarr@tailscale.com>