Currently doing a like then dislike does not give a void karma total. Indeed
karma is removed / added only when the vote hits 1 or -1 but does not correctly
take into account the third (void) state. We also avoid adding karma when
upvoting / downvoting an already upvoted / downvoted slide. Interface does
not allow it but avoiding to add karma at model level is always a good idea.
Karma-related tests are improved a bit.
Commit linked to task ID 1958810 and PR #32057
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>
Thibault Delavallée
02f5b654c3