Fix off by one bug in number of attempts

Fixes bug #2376 with respect to hints.  An earlier bug #641 with regard to 
counting attempts properly for limiting the number of attempts was 
fixed in a similar way.  

The key is that the total number of attempts consists of   incorrect attempts   + correct attempts +  ungraded attempts 

The ungraded attempt (or thisAttempt) is 1 or 0 depending on whether the problem was entered via a submitAnswers request or not.