Fix obtaining packageName in NativePlugin

mobile/src/main/scala/com/github/shadowsocks/plugin/NativePlugin.scala

@@ -1,8 +1,6 @@
 package com.github.shadowsocks.plugin
 
-import android.content.ContentResolver
 import android.content.pm.{PackageManager, ResolveInfo}
-import android.net.Uri
 import android.os.Bundle
 
 /**
@@ -12,8 +10,5 @@ final class NativePlugin(resolveInfo: ResolveInfo, packageManager: PackageManage
   extends ResolvedPlugin(resolveInfo, packageManager) {
   assert(resolveInfo.providerInfo != null)
   override protected def metaData: Bundle = resolveInfo.providerInfo.metaData
-
-  private lazy val uriBuilder: Uri.Builder = new Uri.Builder()
-    .scheme(ContentResolver.SCHEME_CONTENT)
-    .authority(resolveInfo.providerInfo.authority)
+  override def packageName: String = resolveInfo.providerInfo.packageName
 }