rgw/dbstore: Lifecycle support

rgw/dbstore: Lifecycle support

Fixed issues with LC rule processing in dbstore. Also wrt object
transition, for now just the target storage class is updated for that
object in the object table without any other special action taken.

TODO: Once zonegroup, zone and storage-classes can be configured for
dbstore, need to validate target storage-class/placement rules and also
perform any other actions necessary (for eg., moving objects to another
table etc., if in case each storage class needs to have separate object table)

Signed-off-by: Soumya Koduri <skoduri@redhat.com>