Compile apmanager on Android

Noticeable changes to get apmanager to compile on Android:
- Conditional include headers for D-Bus service constants
  based on the target platform.
- Use firewalld proxy instead of permission_broker proxy on
  Android.
- Use stub shill proxy instead of the real one until libshill-client
  is ready.

Bug: 24164800
TEST=Compile apmanager on both Android and Chrome OS
TEST=Run apmanager on Chrome OS device

Change-Id: I7885323796e0043a1e3cc46c129e2736faf4fced
12 files changed