Make the runner tests a go “test”

This change makes the runner tests (in ssl/test/runner) act like a
normal Go test rather than being a Go binary. This better aligns with
some internal tools.

Thus, from this point onwards, one has to run the runner tests with `go
test` rather than `go run` or `go build && ./runner`.

This will break the bots.

Change-Id: Idd72c31e8e0c2b7ed9939dacd3b801dbd31710dd
Reviewed-on: https://boringssl-review.googlesource.com/6009
Reviewed-by: Matt Braithwaite <mab@google.com>
Reviewed-by: David Benjamin <davidben@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/ssl/test/runner/key_agreement.go b/ssl/test/runner/key_agreement.go
index 2ee0087..3a9b899 100644
--- a/ssl/test/runner/key_agreement.go
+++ b/ssl/test/runner/key_agreement.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package main
+package runner
 
 import (
 	"crypto"