Add CtsNetTestCase as presubmit for automotive multi-user multi-display

This changelist adds a new presubmit entry to be used to trigger this test module on automotive target with visible background user enabled (multi-user multi-display targets).

Bug: 374372313
Test: m
Change-Id: I3de5d9660cf472df0011e920c674da0e2895ef39
diff --git a/TEST_MAPPING b/TEST_MAPPING
index b773ed8..c1bc31e 100644
--- a/TEST_MAPPING
+++ b/TEST_MAPPING
@@ -424,6 +424,11 @@
       ]
     }
   ],
+  "automotive-mumd-presubmit": [
+    {
+      "name": "CtsNetTestCases"
+    }
+  ],
   "imports": [
     {
       "path": "frameworks/base/core/java/android/net"