Fix test initialization errors on Q

ConnectivityDiagnosticsManagerTest, MultinetworkApiTest,
NetworkAgentTest crashed before the runner could start them:
 - Ignore ConnectivityDiagnosticsManagerTest on Q: it tests an API that
   was introduced in R.
 - Build JNI libraries used by MultinetworkApiTest against the NDK to
   avoid errors loading the libraries on older platforms, when
   transitive dependencies have been added.
 - Do not attempt to override Handler#getLooper() (which is final) in
   NetworkAgentTest; it appears to have been overridden by accident by
   specifying "val looper" in the TestableNetworkAgent definition, which
   generates a getter.

Test: atest CtsNetTestCasesLatestSdk:ConnectivityDiagnosticsManagerTest
      atest CtsNetTestCasesLatestSdk:MultinetworkApiTest
      atest CtsNetTestCasesLatestSdk:NetworkAgentTest
Bug: 150918852
Change-Id: I262b54c6897ed755adaeb2b118c638320634f7a1
diff --git a/tests/cts/net/jni/Android.bp b/tests/cts/net/jni/Android.bp
index baed48d..3953aeb 100644
--- a/tests/cts/net/jni/Android.bp
+++ b/tests/cts/net/jni/Android.bp
@@ -16,6 +16,7 @@
     name: "libnativedns_jni",
 
     srcs: ["NativeDnsJni.c"],
+    sdk_version: "current",
 
     shared_libs: [
         "libnativehelper_compat_libc++",
@@ -35,6 +36,7 @@
     name: "libnativemultinetwork_jni",
 
     srcs: ["NativeMultinetworkJni.cpp"],
+    sdk_version: "current",
     cflags: [
         "-Wall",
         "-Werror",