[Multi-user] Convert various calls to use user id

Changes various transport, restore and general bookkeeping flows. Also
performs restorecon recursively to relabel child directories properly.

Bug: 121198605
Bug: 121197942
Bug: 121198606
Test: 1) atest RunBackupFrameworksServicesRoboTests
2) user unlocked -> transports registered successfully
3) adb shell bmgr backupnow [package]
4) Cloud restore backup set from 3) -> apps + widgets successful
5) atest BackupManagerTransportAttributesHostSideTest
6) Add secondary user -> check all directories/files relabelled
Change-Id: I26b23fd7bf10b792658fa7c44941be50aee65521