Run "cmd/go terminal test" after standard library tests.
Run "testing race detector" before cgo tests, not in the middle of them.

Fixes #21524

Change-Id: I32964ec6377dd070242138ec452bd8ab1821dcc5
Reviewed-on: https://go-review.googlesource.com/57230
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Joe Tsai <joetsai@google.com>