[Test] Add more checks in IPv6LinkLocalWithDefaultRoute

A follow-up commit to aosp/2162116. Check if DNS resolver starts to send
AAAA queries as well as A queries when IPv6 global address is added to
the network interface.

Bug: 203748535
Bug: 238583316
Test: atest
Change-Id: Ia49140df20fd225b101967d08da94e327d64b0cf