Clean up unused codes around the RemoteUserInfo

RemoteUserInfo doesn't require IBinder for finer grained identification
among MediaControllers in the same process/package. So extra information
don't need to be shared across the processes.

Bug: 146815343
Test: Build
Change-Id: I6935c9c43b5fdfa0c608c753779e17b6cf0d341e
6 files changed