veyron/tools/servicerunner: Use t.Fatalf directly instead of through a helper.
veyron/tools/servicerunner: Use t.Fatalf directly instead of through a helper.

When you use it in a helper function the error prints the line number of the
helper function, which doesn't tell you where the error was.

Change-Id: I515d90ac1d5bf12ee3684f3806abdcb95330fa0c

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