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

We set the timeout for every version yes, but the timeout expires only on versions <32. On versions >= 32 the Custom MozUITour Event will be triggered first which will cancel the timeout [0]. 

I use this timeout trick to workaround versions < 32 which will ignore the Custom Event. 

[0] https://github.com/mozilla/snippets-service/pull/64/files#diff-3adb3669370af06c37adc916ba7b7c3cR49

Setting the cache until the next time they hit about:home is like caching for value in case the user reloads about:home?