Add presubmit for com.android.internal.net

Follow up of aosp/2855538 to run FrameworksNetTests in presubmit.

Test: atest
Test: presubmit
Change-Id: I4d21c9918a2dc62555d5fab307aaf86123da0502

core/java/com/android/internal/net/TEST_MAPPING

 {
-  "postsubmit": [
+  "presubmit": [
     {
       "name": "FrameworksNetTests",
       "options": [