Use eventually expect to wait for blocked status change

While the test case was running, if the network condition changes,
e.g. IPv6 RA received, the test case would fail since unexpected
LinkPropertiesChanged event was received, while blockedStatusChanged
event was expected.

Make the test wait for the expected event and ignore others to make
the test more robust.

Test: atest android.net.cts.ConnectivityManagerTest#testBlockedStatusCallback \
      --rerun-until-failure 100
Fix: 242833720
Change-Id: Ic3cd47773955d27445511dbd94733f91e3037596
1 file changed