Add TEST_MAPPING to android/server/security directory

This CL adds a presubmit check to
services/core/java/com/android/server/security directory.

The ApkVerityTest Test is executed as presubmit check everytime that
VerityUtils.java file is modified.

Bug: 146676114
Test: Tested locally.
$ cd services/core/java/com/android/server/security
$ atest
And verified that ApkVerityTest was executed

Change-Id: I6d652ebebaa1fd8872dda6bdffec03335dd3007d

services/core/java/com/android/server/security/TEST_MAPPING

@@ -0,0 +1,8 @@
+{
+  "presubmit": [
+    {
+      "name": "ApkVerityTest",
+      "file_patterns": ["VerityUtils\\.java"]
+    }
+  ]
+}