veyron/runtimes/google/ipc: Fix flaky test
veyron/runtimes/google/ipc: Fix flaky test

This should fix failures like:
--- FAIL: TestProxy-16 (3.97 seconds)
	server_test.go:170: Got (, ipc: response header decoding failed: EOF) want ("", "RESOLVE: <err>") as proxy is down

(https://www.envyor.com/jenkins/job/veyron-go-race/1874/console)

Change-Id: I61025994c29550b2dc0039b2c0f9566d3fde58e2

vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref