Add the test for nat64 prefix discovery bypass tls

This test is added to make sure the fix of aosp/836502
won't be broken.

Bug: 119992869
Test: runtest passed
Merged-In: Ibc860d6d53fdbb1e75aebed9c6be0c9d9554edb3
Merged-In: I419de52e9ef5cc49d168153d2cb4d6e5b2462cbe
Change-Id: I69d603b3905a688c0361a73598c536c9223ba6a9
(cherry picked from commit 76256d06)