Ignore No Data Changed Notifications

We're adding a "No Data Changed" notification to the framework for
K/V backups where no data has changed. LocalTransport has no use
for this notification so we'll ignore it if we see it.

Test: m -j RunBackupFrameworksServicesRoboTests
Bug: 147481066
Change-Id: Ida934f2a17367c430f3411ce1a457515c59746fd