TestLookupAutoPathErratic sometimes fail on TravisCI saying below

```
=== RUN   TestLookupAutoPathErratic
--- FAIL: TestLookupAutoPathErratic (8.30s)
    erratic_autopath_test.go:39: Test 0, failed to sent query: "read udp [::1]:39758->[::1]:56643: i/o timeout"
FAIL
```

The failure happens when Google replies slowly.
This PR changes to not use Google but run CoreDNS locally and proxy to the server.

---

Because the failure depends on Google, sometimes it happens frequently but sometimes it doesn't happen.
I hope following test help you reproduce it.

```
func TestLookupAutoPathErratic2(t *testing.T) {
	for i := 0; i < 200; i++ {
		TestLookupAutoPathErratic(t)
	}
}
```

or I can reproduce it by changing proxy to other DNS like 1.1.1.1 instead of 8.8.8.8 too