disable syncing of trustedList from PZP to PZH

fixes bug where an empty trustedList is synced to PZH (right after
enrollment) overriding the info of the existing PZH there, which made it
impossible for other PZPs to join this PZH.
Merge pull request #83 from aldafu/disable-trustedlist-sync-to-pzh

disable syncing of trustedList from PZP to PZH