Select staff only from the branch office

@vishwas,

Assigning staff has three entry points

1) Creating client/group/center/loan/saving
2) Updating/Editing client/group/center/loan
3) Assign staff api for client/group/center/loan

I had missed to updating staffInSelectedOfficeOnly:true for 3rd entry point.
And this pull request is fix for the same.

Also I noticed, there is no option to update staff for saving account. Asked Subbu to look into it.