Move calls using *testing.T out of dgroup.Go() call.
Move calls using *testing.T out of dgroup.Go() call.

The `dgroup.Go()` starts a new goroutine. A `t.Fatal()` calls
goexit which bypasses the dgroup's clean-up. A subsequent `Wait()` for
the group would then hang forever.

datawire/telepresence,datawire/telepresence,datawire/telepresence