Fix problem for download cancelling when deleting channels

Merge some minor fixes (indentation in services.py and use
episode.url instead of episode.link in gui.py) from the 0.12.2
release branch.

src/gpodder/gui.py

@@ -1920,7 +1920,7 @@ class gPodder(GladeWidget):
                 # cancel any active downloads from this channel
                 if not delete_partial:
                     for episode in self.active_channel.get_all_episodes():
-                        services.download_status_manager.cancel_by_url(episode.link)
+                        services.download_status_manager.cancel_by_url(episode.url)
 
                 # get the URL of the podcast we want to select next
                 position = self.channels.index(self.active_channel)

src/gpodder/services.py

@@ -409,7 +409,7 @@ class DownloadStatusManager(ObservableService):
             thread = self.status_list[element]['thread']
             if thread is not None and thread.url == url:
                 self.remove_download_id( element)
-    	        return True
+                return True
 
         return False