Add imports to networking test mapping

Ensure that appropriate networking tests are triggered when submitting
changes in the frameworks/base directories.

Change-Id: Ibf8b567fa7721299120b0a6c6836dd770d92a9fc
Test: treehugger runs TEST_MAPPING tests

core/java/android/net/TEST_MAPPING

@@ -0,0 +1,20 @@
+{
+  "imports": [
+    {
+      // Also includes cts/tests/tests/net
+      "path": "frameworks/base/tests/net"
+    },
+    {
+      "path": "packages/modules/NetworkStack"
+    },
+    {
+      "path": "packages/modules/CaptivePortalLogin"
+    },
+    {
+      "path": "frameworks/base/packages/Tethering"
+    },
+    {
+      "path": "frameworks/opt/net/wifi"
+    }
+  ]
+}

services/net/TEST_MAPPING

@@ -0,0 +1,7 @@
+{
+  "imports": [
+    {
+      "path": "frameworks/base/core/java/android/net"
+    }
+  ]
+}

tests/net/TEST_MAPPING

@@ -8,5 +8,10 @@
     {
       "name": "FrameworksNetDeflakeTest"
     }
+  ],
+  "imports": [
+    {
+      "path": "cts/tests/tests/net"
+    }
   ]
 }