Added more logging to diagnose a racy runtime restart.

Also fixed a possible NPE on saveLocked() and improved locking.

Test: cts-tradefed run commandAndExit cts-dev -m CtsAutoFillServiceTestCases
Bug: 65374274

Merged-Id: I4b8368a9d19b4b4da76533dadb013ff2e2922955
Change-Id: I4b8368a9d19b4b4da76533dadb013ff2e2922955