Add CTS tests for cleartext traffic default change

Cleartext traffic permitted now defaults to False for apps targetting P,
this test splits the previous cleartext test into pre-P and P+ targetSDK
versions.

Tests which depended on cleartext traffic have been opted in to
cleartext traffic.

Test: This is the test
Bug: 63931636
Change-Id: I5c4aa39e4055380a54bfe09f668894240be713f8
diff --git a/tests/cts/net/AndroidManifest.xml b/tests/cts/net/AndroidManifest.xml
index dd310a1..37bf323 100644
--- a/tests/cts/net/AndroidManifest.xml
+++ b/tests/cts/net/AndroidManifest.xml
@@ -30,7 +30,7 @@
     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
     <uses-permission android:name="android.permission.WRITE_SECURE_SETTINGS" />
 
-    <application>
+    <application android:usesCleartextTraffic="true">
         <uses-library android:name="android.test.runner" />
         <uses-library android:name="org.apache.http.legacy" android:required="false" />