Add simple fake for native service manager.

Reusing the existing binder-based native service manager has
proved problematic in host/test environments.

So as a workaround, this commit creates a IServiceManager native
implementation that can be communicated with directly.

Bug: 147595993
Test: m fakeservicemanager_test; fakeservicemanager_test
Change-Id: Icfa6f2fd314bd5a7b3d5e8a064b487f92b99b133