Bug 1501024 WifiScanner should use ApplicationContext r=JanH

Fixed lint warning regarding memory leak inside WifiManager constructor.

Differential Revision: https://phabricator.services.mozilla.com/D13930

--HG--
extra : moz-landing-system : lando

mobile/android/stumbler/java/org/mozilla/mozstumbler/service/stumblerthread/scanners/WifiScanner.java

@@ -4,6 +4,7 @@
 
 package org.mozilla.mozstumbler.service.stumblerthread.scanners;
 
+import android.annotation.SuppressLint;
 import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
@@ -211,6 +212,7 @@ public class WifiScanner extends BroadcastReceiver {
         return true;
     }
 
+    @SuppressLint("WifiManagerPotentialLeak")
     private WifiManager getWifiManager() {
         return (WifiManager) mContext.getSystemService(Context.WIFI_SERVICE);
     }