Return USER_OP_SUCCESS when force stopping a user

Bug: 26379502
Change-Id: I08dc18eec5b8dccf63a806acc9b3bfda890ceedb
diff --git a/services/core/java/com/android/server/am/UserController.java b/services/core/java/com/android/server/am/UserController.java
index 20b1e60..6e51316 100644
--- a/services/core/java/com/android/server/am/UserController.java
+++ b/services/core/java/com/android/server/am/UserController.java
@@ -304,7 +304,10 @@
                         + relatedUserId);
                 // We still need to stop the requested user if it's a force stop.
                 if (force) {
+                    Slog.i(TAG,
+                            "Force stop user " + userId + ". Related users will not be stopped");
                     stopSingleUserLocked(userId, callback);
+                    return USER_OP_SUCCESS;
                 }
                 return USER_OP_ERROR_RELATED_USERS_CANNOT_STOP;
             }