[Multi-user] Change Trampoline,BackupManagerService to use userId

Also, a few additional small changes:
1) move getTransportWhitelist from UserBackupManagerService to
BackupManagerService since it doesn't depend on the user
2) remove setBackupProvisioned from BackupManagerService and
UserBackupManagerService since its unused and is a no-op. I'll remove
it from Trampoline and the AIDL in a future CL.

Bug: 120120742

Test: 1) atest RunBackupFrameworksServicesRoboTests
2) atest $(find \
frameworks/base/services/tests/servicestests/src/com/android/server/backup \
-name '*Test.java')
3) atest CtsBackupTestCases
4) atest CtsBackupHostTestCases
5) atest GtsBackupTestCases
6) atest GtsBackupHostTestCases
7) 'adb shell bmgr' enabled/backupnow flow

Change-Id: Iec932dac2ccd6200888e22b35a524a2aec834854
5 files changed