[fix bug 1066865] Ignore snippets that link to about:accounts when sync is setup.

Yeah I'm not a big fan of this timeout either but on the other hand this is only used on firefox versions <32 which have a ever shrinking share as days pass. Also I'm pretty confident we can reduce this to something like 100ms so it doesn't alter the user experience.

Caching the value brings up the problem of how long would you cache it. A month (like geocaching) feels like a lot for this option, maybe we cache for 5 or 10 days?