vp-nextfitruncard should not give you pre-processing range which fails integrability

Created by: wilsonmr

as per https://github.com/NNPDF/nnpdf/pull/1007#issue-520429435

Also, I noticed that the small-x preprocessing range for T8 is set to [0.7167,1.102]. I think that, as discussed few month ago, we should set it to [0.7167,1.00], otherwise it s not compatible with integrability.

we should probably have the iterated runcard be wrong