Run all executors in background

app/src/main/java/eu/faircode/email/EntityLog.java

@@ -49,7 +49,7 @@ public class EntityLog {
     @NonNull
     public String data;
 
-    private static ExecutorService executor = Executors.newSingleThreadExecutor();
+    private static ExecutorService executor = Executors.newSingleThreadExecutor(Helper.backgroundThreadFactory);
 
     static void log(Context context, String data) {
         Log.i(Helper.TAG, data);

app/src/main/java/eu/faircode/email/FragmentMessages.java

@@ -88,7 +88,7 @@ public class FragmentMessages extends FragmentEx {
     private SearchState searchState = SearchState.Reset;
     private BoundaryCallbackMessages searchCallback = null;
 
-    private ExecutorService executor = Executors.newCachedThreadPool();
+    private ExecutorService executor = Executors.newCachedThreadPool(Helper.backgroundThreadFactory);
 
     private static final int MESSAGES_PAGE_SIZE = 50;
     private static final int SEARCH_PAGE_SIZE = 10;