Address comments and final cleanup from refcounting integration

Added some extra comments on reference counting and moved a few methods
around. No significant logical changes made in this CL

Bug: 63409385
Test: CTS, Unit tests (both frameworks-base and netd) and binder tests
all pass

Change-Id: I89f1f4a021db48ae406fefefa6aca7406045736c
2 files changed