[Dnssec-trigger] Timer/timeout for hotspot mode and reprobe

[Phil Regnauld]

Running the latest and greatest version on OX X 10.9

Occasionnally, I have to disable dnssec validation by going into Hotspot Signon
mode. But I realized that I hadn't reenabled it in a few weeks !

Question (before I dig into the source):

- do I remember wrongly or didn't dnssec-trigger use to attempt to
  reprobe when changing networks ?

- if not, shouldn't it ?

- somewhat related, wouldn't it be smart to have some kind of
  configurable timer (or option when selecting Hotspot Signon),
  for instance:

  Remind me in 1 hour / 1 day / Until I say so.

Cheers,
Phil