veyron/services/mgmt/logreader/impl: Fix race in test.
veyron/services/mgmt/logreader/impl: Fix race in test.

Change-Id: I70f678c77788c39f60a11a55c49652a4739e2ffd

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