Refine #530 again and again

Put ShadowsocksRunnerService into :bg process. It helped to solve #530, but
still I'm not sure why it works.

One assumption is that the startService() in BootReceiver helps to ensure :bg
process in a valid state.

src/main/AndroidManifest.xml

@@ -118,6 +118,7 @@
 
         <service
                 android:name=".ShadowsocksRunnerService"
+                android:process=":bg"
                 android:exported="false">
         </service>
 

src/main/scala/com/github/shadowsocks/ShadowsocksRunnerService.scala

@@ -54,11 +54,11 @@ class ShadowsocksRunnerService extends Service with ServiceBoundContext {
   }
 
   override def onServiceConnected() {
-    handler.postDelayed(() => if (bgService != null) {
+    if (bgService != null) {
       if (app.isNatEnabled) startBackgroundService()
       else if (VpnService.prepare(ShadowsocksRunnerService.this) == null) startBackgroundService()
-      stopSelf()
-    }, 1000)
+    }
+    handler.postDelayed(() => stopSelf() , 1000)
   }
 
   def startBackgroundService() = {