Wait for process completion before reading stdout/stderr buffers to eliminate race between I/O Go routines and test cleanup. Updates golang/go#74437 Cq-Include-Trybots: luci.golang.try:x_crypto-gotip-linux-amd64-longtest-race Change-Id: I2e650c04db5be0d7a1e858ce40e25f13ad12223c Reviewed-on: https://go-review.googlesource.com/c/crypto/+/693596 Auto-Submit: Daniel McCarney <daniel@binaryparadox.net> Reviewed-by: Roland Shoemaker <roland@golang.org> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>