Add a keep connected for test reason

This has been sorely needed for a while. Instead of filing requests
for each of your networks in a CSTest, which is fiddly at best and
sometimes almost impossible (because you can't single out the network),
you can now add this flag and be done with it.

Test: CSKeepConnectedTest
Change-Id: Ie168fe1f3a17de035fdf05e3d6580d3262a3448e

framework/src/android/net/NetworkScore.java

@@ -44,7 +44,8 @@ public final class NetworkScore implements Parcelable {
     @Retention(RetentionPolicy.SOURCE)
     @IntDef(value = {
             KEEP_CONNECTED_NONE,
-            KEEP_CONNECTED_FOR_HANDOVER
+            KEEP_CONNECTED_FOR_HANDOVER,
+            KEEP_CONNECTED_FOR_TEST
     })
     public @interface KeepConnectedReason { }
 
@@ -57,6 +58,12 @@ public final class NetworkScore implements Parcelable {
      * is being considered for handover.
      */
     public static final int KEEP_CONNECTED_FOR_HANDOVER = 1;
+    /**
+     * Keep this network connected even if there is no outstanding request for it, because it
+     * is used in a test and it's not necessarily easy to file the right request for it.
+     * @hide
+     */
+    public static final int KEEP_CONNECTED_FOR_TEST = 2;
 
     // Agent-managed policies
     // This network should lose to a wifi that has ever been validated