Set correct permissions after importing disk

Importing a qcow2 file without converting it potentially has the wrong permissions, this will cause problems when eg. saving the disk as a template. Fix it by setting the correct permissions explicitly.

disk.py

@@ -291,6 +291,8 @@ class Disk(object):
                            downloaded_file,
                            self.get_path()]
                 subprocess.check_output(cmdline)
+
+            os.chmod(self.get_path(), 0o644)
         except AbortException:
             if os.path.exists(downloaded_file):
                 os.unlink(downloaded_file)