Do not delete input after sign & encrypt

* src/cryptcontroller.cpp (CryptController::do_crypto): Do
not delete input after constructing MIME.

After sign & encrypt we removed the input as we converted
it into a mimestructure. But that would throw it away for
the second try. In case we call do_crypto again with
the force parameter.

• GnuPG-Bug-Id: T6701