When (re-)sharing an incomming federated share set the corrent owner

Incomming federated shares are a special kind. We mount them as normal
webdav shares but we do supply owner info with the federated cloud id of
the share owner.

Since we do not yet have the new resharing behaviour on federated shares
we need to set the correct owner. Which will allow sharing and proper
mounting for other users.

fixes #22500