Only mark existent remote files as superseded

Signed-off-by: Andrej Shadura <andrew.shadura@collabora.co.uk>

osc_plugin_dput/main.py

@@ -205,6 +205,7 @@ def do_dput(self, subcmd, opts, *args):
                 remote_dsc = Dsc(osc.core.streamfile(u, bufsize='line'))
 
                 for entry in remote_dsc.get('Files'):
+                    if entry['name'] in remote_file_list:
                         superseded.add(entry['name'])
 
                 superseded.add(f)