`TestTracingHTTPTimeout` still flakes in CI after #35101, failing at the
POST:
--- FAIL: TestTracingHTTPTimeout (0.26s)
tracing_test.go:633: request: Post "http://127.0.0.1:43497": EOF
The test sets a short server `WriteTimeout` and posts a blocking call.
`ContextRequestTimeout` leaves a fixed 100ms for the server to write its
timeout response before the HTTP write deadline cuts the connection.
I can't repro it locally, but my theory is that under load that write
can miss the window, so the connection is dropped and the client POST
returns `EOF`, failing the test before it inspects the span. This is the
only test exposed to it because it is the only one that configures a
`WriteTimeout`.
The EOF is benign: the server sets the timeout error on the SERVER span
before attempting the write, independent of whether the client receives
the response. Since that span status is all the test asserts,
`tryPostJSONRPC` tolerates the transport error instead of failing on it.
a326298f51