Add end-to-end testing for conflicts happening during and after probing.
This includes making sure that interfaces have a usable IPv6 address
before starting each test, as mdnsresponder would not probe on the
interface if the address is not present, and would go straight to
advertising otherwise.
Bug: 266151066
Test: atest NsdManagerTest
Change-Id: Ie1a1e888afbcd5c1bafaf218a98ac4c2f5fe63ee
0d75d977a2