Export AIDL files as a filegroup for services.jar

Put AIDL files into a filegroup so they can be imported as sources
for services.jar.

Test: m checkbuild

Change-Id: I1bdb0d2e08836500fce588b496f25c2d74fc9c91
diff --git a/server/Android.bp b/server/Android.bp
index c304388..341f510 100644
--- a/server/Android.bp
+++ b/server/Android.bp
@@ -3,3 +3,9 @@
     name: "netd_aidl",
     srcs: ["binder/android/net/INetd.aidl"],
 }
+
+// AIDL interface between netd and services.core
+filegroup {
+    name: "netd_metrics_aidl",
+    srcs: ["binder/android/net/metrics/INetdEventListener.aidl"],
+}