Add BackupUtils#waitUntilBackupServiceIsRunning

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

Bug: 131307343
Test: atest BackupUtilsTest

Merged-In: I6998821a8d57e5394931d03c3921c510bacc4c79
Change-Id: I6998821a8d57e5394931d03c3921c510bacc4c79
(cherry picked from commit 53f946db82226fe9c71750919323196a4f7ce61d)
3 files changed
tree: 9f7b94edc93d634a6b3d6eefa7beea610cf83d53
  1. build/
  2. common/
  3. tools/
  4. OWNERS
  5. PREUPLOAD.cfg
  6. test_defs.sh