Make sure DomainChoiceFields are on data mode

If that domain is empty (for example, no clients or no addresses on a new
database), kiwi would not set data mode for us, so force it or else it would
allow any string on that entry.

Change-Id: I24765033d288ab6fc103231a79b961dd76907f39
Make sure branch is set to the station

Since set_current_branch_station always receive the default_store, which will
never be committed, that information was being lost. Make sure we link both
objects on a new store and really commit them.

Change-Id: I46445a3f130c655c2a3c03d50d3660577abf63a4
(cherry picked from commit 86af17fe4b3b7d1b36dd27810e12be1a666a9f98)