Add dumpsys param to dump users running backup service

This is required in CTS tests to know when UserBackupManagerService init is finished.

Bug: 131307343
Test: 1) atest RunBackupFrameworksServicesRoboTests
      2) atest CtsBackupTestCases
      3) atest CtsBackupHostTestCases
      4) atest GtsBackupTestCases
      5) atest GtsBackupHostTestCases

Change-Id: Ia220f32b5be793b3b36efb2985604e29b0015e53