Fix testNightModeAutoNotPersistedCarMode

Fixing UiModeManagerTest#testNightModeAutoNotPersistedCarMode on devices
with locked night mode.

Bug: 159700716
Bug: 159686230
Test: atest UiModeManagerTest#testNightModeAutoNotPersistedCarMode
Change-Id: I7eeb46beb61ad1d9d1df9ab379347bcb86770150
diff --git a/tests/app/src/android/app/cts/UiModeManagerTest.java b/tests/app/src/android/app/cts/UiModeManagerTest.java
index 7174f36..e877350 100644
--- a/tests/app/src/android/app/cts/UiModeManagerTest.java
+++ b/tests/app/src/android/app/cts/UiModeManagerTest.java
@@ -124,6 +124,10 @@
     }
 
     public void testNightModeAutoNotPersistedCarMode() {
+        if (mUiModeManager.isNightModeLocked()) {
+            return;
+        }
+
         // Reset the mode to no if it is set to another value
         setNightMode(UiModeManager.MODE_NIGHT_NO);
         mUiModeManager.enableCarMode(0);