[FLAKE] xds_end2end_test "Value of: locality_picked_rates"

This failure looks rather interesting. Seems the range is not large enough.

```
test/cpp/end2end/xds_end2end_test.cc:1542
Value of: locality_picked_rates[i]
Expected: (is >= 0.177778) and (is <= 0.266667)
  Actual: 0.27 (of type double)
```