Mark flaky tests as @Ignore.

This is to make sure the behavior is consistent locally, on apct,
and on treehugger. Also marking a couple of tests as @FlakyTest.

Test: runtest --path frameworks/opt/telephony/tests/telephonytests
Bug: 29579544
Change-Id: I75b4d12a0c84d5629cf4b6646ea0e5a35bd2bf71