Make Connection.Listener methods package private.

To prevent using these outside of the API surface, making package private
so we don't get tempted to use in the framework.

Bug: 141576016
Test: Manual smoke test.
Test: Run unit tests.
Test: Run CTS tests.
Change-Id: Ife3a82371b018b74efbe10e11015526d7aaeb7a9
1 file changed