APN Editor: No animation or feedback when switching Internet APNs

When multiple Internet APNs are listed in the APN Editor, when a user taps an Internet APN name, an activation is triggered, however it isn't very clear to the user what's happening. The check next to the currently connected APN disappears, and if the new activation request succeeds, then the check appears next to the new APN.

<https://wiki.ubuntu.com/Networking#apn-mobile>: "If you tap “Activate”, progress and success/failure feedback should be shown in the same way as connecting to Wi-Fi. Everything in the dialog except for “Cancel” should become insensitive, and “Activate” should change to a spinner until activation completes."