veyron/lib/testutil/blackbox: allow for use from outside of tests.
veyron/lib/testutil/blackbox: allow for use from outside of tests.

Change-Id: Ib0cac546e4d7e881a8eda53c020af3f5beb370a8

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