DscpPolicyTest does not have an IpClient, so it relies on assigning the
LinkAddresses at interface creation. If DAD is enabled, the global
address cannot be used immediately, so the test packet selects the wrong
source address. There is no obvious way to fix this without disabling
DAD as the TestableNetworkCallback receives the LinkProperties update
before the address can be used.
This functionality will also be useful in ethernet tests, which
currently have to block for a long time.
Test: atest DscpPolicyTest
Bug: 235559605
Change-Id: Id7788df5e92ebd8eaf4619a23f44135ea4a2144e
336bb5cf6d