Setup tab of AdminCenter does only saves the last changeset

When administrator edits the email information in Setup tab, some information are reinitialized when user clicks on "Save" button.

Steps to reproduce:
1. In Setup tab of Admin Center, edit the "Email notifications subject prefix" and " Host name for SMTP" values.
2. Click "Save".
-> Values are correctly saved.
3. Edit "Sender address mail".
4. Click "Save".
-> "Email notifications subject prefix" and "Host name for SMTP" are back to default values ([Nuxeo] and localhost).
5. Click "Save".
-> "Sender address mail" is back to default.