Updating proto enums.

Updating proto enums to differentiate between the internal job stop
reasons and the public stop reasons.

Bug: 138239687
Bug: 171305774
Test: make statsd_testdrive && ./out/host/linux-x86/bin/statsd_testdrive 8
Test: atest frameworks/base/services/tests/servicestests/src/com/android/server/job
Test: atest frameworks/base/services/tests/mockingservicestests/src/com/android/server/job
Test: atest ContentResolverTest (all)
Test: atest CtsJobSchedulerTestCases
Test: atest CtsSyncManagerTest
Test: atest SyncManagerTest
Test: atest SyncOperationTest
Test: atest SyncRequestTest
Change-Id: I8d51c4dfb57d52e9c507437107afbad48cc9cecd