Do lazy init of BMS at the beginning of every BackupManager method

Bug: 124379585
Test: 1) atest RunBackupFrameworksServicesRoboTests
      2) atest CtsBackupTestCases
      3) atest CtsBackupHostTestCases
      4) atest GtsBackupTestCases
      5) atest GtsBackupHostTestCases

Change-Id: I86857a6ee21862384c089e458ae0b6bd18538b57
1 file changed