core: introduce update method to LunDAO

* Added update method to LunDAO and LunDaoDbFacadeImpl.
* Added stored procedure to storages_san_sp.sql.
* Replaced current usages of updateLUNsDeviceSize and
  updateLUNsVolumeGroupId with update.
* Modified tests accordingly.

Change-Id: Ie0391443313a6ff065f08e0204f95b4980c01e02
Related-To-Bug-Url: https://bugzilla.redhat.com/1026868
Signed-off-by: Daniel Erez <derez@redhat.com>