Make the postrm script output the uninstall message only when uninstalling.
Make the postrm script output the uninstall message only when uninstalling.

This fixes: https://github.com/globaleaks/GlobaLeaks/issues/602

vodkina/GlobaLeaks,vodkina/GlobaLeaks,vodkina/GlobaLeaks,vodkina/GlobaLeaks