Android: Fix sign package behavior

Ensure that the widget and the step's settings are in sync with each
other. Also don't restore the sign state since that leads to a password
prompt on restoring the project.

Task-number: QTCREATORBUG-10835
Change-Id: I4c3ead74e8caa6c87096c13173530a9c8ccae6aa
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>