Move rollback manager implementation to RollbackManagerServiceImpl

So that RollbackManagerService extends SystemService as per convention
and RollbackManagerServiceImpl need not be made public.

Bug: 112431924
Test: atest RollbackTest
Change-Id: I85d2fd27e4705637d5fb7342d9389ef12f869fc9
diff --git a/services/java/com/android/server/SystemServer.java b/services/java/com/android/server/SystemServer.java
index 855fb50..be09aea 100644
--- a/services/java/com/android/server/SystemServer.java
+++ b/services/java/com/android/server/SystemServer.java
@@ -783,7 +783,7 @@
 
         // Manages apk rollbacks.
         traceBeginAndSlog("StartRollbackManagerService");
-        mSystemServiceManager.startService(RollbackManagerService.Lifecycle.class);
+        mSystemServiceManager.startService(RollbackManagerService.class);
         traceEnd();
     }