selectBackupTransportAsync should report failure when backup is not available

Merged-in: I393308857ea6082dca167e3e417b946615a83c20
Fix: 37304539
Test: runtest -x frameworks/base/services/tests/servicestests/src/com/android/server/backup/TrampolineTest.java
Test: setup device owner, then set up profile.
      Ensure tapping Settings->Google->Work->Security -> Verify app
      is working

Change-Id: I88c3e3163605d62123c88377ae0843084e354212