Rollbacks shouldn't be removed when it session expires (1/n)

Once a rollback is made available, the status of its associated session
no longer matters.

Bug: 185132440
Test: Will be added in next CL
Test: atest StagedRollbackTest
Change-Id: I3c2b718905d2d7619d6f299ee5402fd858de030e

services/core/java/com/android/server/rollback/RollbackManagerServiceImpl.java

@@ -613,9 +613,11 @@ class RollbackManagerServiceImpl extends IRollbackManager.Stub implements Rollba
                 PackageInstaller.SessionInfo session = mContext.getPackageManager()
                         .getPackageInstaller().getSessionInfo(rollback.getStagedSessionId());
                 if (session == null || session.isStagedSessionFailed()) {
-                    iter.remove();
-                    deleteRollback(rollback,
-                            "Session " + rollback.getStagedSessionId() + " not existed or failed");
+                    if (rollback.isEnabling()) {
+                        iter.remove();
+                        deleteRollback(rollback, "Session " + rollback.getStagedSessionId()
+                                + " not existed or failed");
+                    }
                     continue;
                 }