On Windows, if we write to our socket and then close it, the peer sometimes
doesn't get all the data. This was working for our shimShutsDown tests because
we send close_notify in parallel with the peer and sendAlert(alertCloseNotify)
did not internally return an error.
For convenience, sendAlert returns a local error for non-close_notify alerts.
Suppress that error to avoid the race condition. This makes it behave like the
other shimShutsDown tests.
Change-Id: Iad256e3ea5223285793991e2eba9c7d61f2e3ddf
Reviewed-on: https://boringssl-review.googlesource.com/7980
Reviewed-by: Adam Langley <agl@google.com>
4d559617cd