nested transaction for createMemberSync

Nested transaction for membersManagerBl().createMemberSync

It fixes problem caused by 09add5b4748d229187b30d27f75008b65fec5094
(New Synchronizer workflow) - There is caught exception from
createMemberSync wich is not throw out. Therefore there is no rollback
and by that the inconsistency in database is made (member is created but
he is not in members group).