2.3 NTP UI error

[q54e3w]

Adding time servers beyond three causes them to be added to config.xml correctly (at least in my basic testing) but the UI elements > 3 disappear when applying the changes.

[phil.davis]

This should do it: https://github.com/pfsense/pfsense/pull/2186

Note that the code also needs some limit on the number of rows that can be added - there is a maximum of 10 time servers saved. So the Add button should be hidden once there are 10 rows shown.