[Tizen] Don't not execute preun section when we uppdate crosswalk rpm

This lead to break installation througth backend (symbolic link are removed)

BUG=XWALK-2699
Signed-off-by: Baptiste DURAND <baptiste.durand@open.eurogiciel.org>
Merge pull request #2490 from eurogiciel-oss/XWALK-2699

Don't not execute preun section when we uppdate crosswalk rpm