Put kernel net tests in presubmit.

Test: treehugger
Change-Id: I988f82ae312a23f0d7c940f9e8370c71a0d165c7
diff --git a/net/test/TEST_MAPPING b/net/test/TEST_MAPPING
new file mode 100644
index 0000000..8d31caa
--- /dev/null
+++ b/net/test/TEST_MAPPING
@@ -0,0 +1,7 @@
+{
+  "presubmit": [
+    {
+      "name": "vts_kernel_net_tests"
+    }
+  ]
+}