Add resolv_unit_test_config.xml for mts

MTS can't find the multiarch test binary correctly.
This xml file is used to let MTS know which test binary should be took.
It is a temporary solution, hopefully we can get rid of the xml soon.

Bug: 151122604
Test: forrest
Change-Id: I45e45912f91e8d78891a8658f9f2e27c7e6252da
diff --git a/Android.bp b/Android.bp
index b54cf1d..cd659d8 100644
--- a/Android.bp
+++ b/Android.bp
@@ -178,6 +178,7 @@
     name: "resolv_unit_test",
     test_suites: ["device-tests", "mts"],
     require_root: true,
+    test_config: "resolv_unit_test_config.xml",
     //TODO:  drop root privileges and make it be an real unit test.
     defaults: ["netd_defaults"],
     srcs: [