borg: Don't reconnect early into manual backups

The rationale is this: When clicking the button and immediately being thrown into the reconnection loop it's probably better to instead inform the user about the error and just abort. The user is very likely present and probably doesn't want to wait 10 minutes just to get the notification that the backup has failed due to a connection problem.

We don't want to do this for scheduled backups of course. And also not after some time has elapsed as this both increases the chance of the user having left the device and also increases the chance this is not a permanent connection issue but rather a problem that has occurred after the backup has already started.

Closes #396 (closed) (at least the part of it that is possible to fix, what even is a permanent error, with networking almost everything can break)