[KV] PerformBackupTask => KeyValueBackupTask

Test: atest RunFrameworksServicesRoboTests
Test: adb shell bmgr backupnow com.google.android.apps.backupapp
Test: adb shell bmgr backup com.google.android.apps.backupapp
      adb shell bmgr run
Test: atest ScheduledBackupHostSideTest

Change-Id: I30b689538e6301d05416e21abe012a51ef83c5df
6 files changed