Separate Host Reservation DHCP options are not displayed after editing until refresh.

The issue was reported by @slawek during 1.10 sanity checks. Source.

Separate Host Reservation DHCP options are not displayed after editing until refresh.

Steps to reproduce:

1. Add host reservation with the Configure individual server values. switch unchecked. Assign to it any DHCP option.
2. Edit the reservation, enable the above switch, and change the DHCP option value for one server.
3. Open the edited host reservation page.
4. Observe that the single DHCP option panel is displayed.