build: Set Fresnel scenario run count to 7

build: Set Fresnel scenario run count to 7

I've got a few weeks worth of data for runs=5 from which
I can check how often time-based values had false negatives.
Let's see if runs=7 performs better (more evenly distributed
between faster and slower), or worse (more likely to get a
super slow result that is otherwise absent).

Change-Id: I38e9b4c2c3c2f4832fc0e9244a00a723510d295f