Change score calculation for functest reporting

the goal is not to penalize scenario with few iteration due to
CI pipeline constraints
until now the top score was calculated on the base on 4 iterations, it means
whatever the number of iterations, we always consider the possible top score
based on at least 4 iterations

each case can get
- 3 points (last 4 iterations PASS)
- 2 points (more than 1 PASS over the last 10 days but 1 FAIL of the last 4)
- 1 point (at least 1 PASS over the last 10 days)
- no point  (never work)

so if we consider a scenario with 10 cases, the top score is
30 = 10*3 (max points)

the coefficient to calculate the top score is not the number of iterations

- 1 iteration => possible  top score 10
- 2 iterations  => top score 20
- 3 iterations => top score 20
- 4 or more iterations => top score 30

previously top score was systematically 30

https://wiki.opnfv.org/plugins/servlet/mobile#content/view/6828617

Change-Id: I01102bc00766b7f5b58e73befa7d5328fcc895cc
Signed-off-by: Morgan Richomme <morgan.richomme@orange.com>