TST: optimize: mark two linprog tests for skipping
TST: optimize: mark two linprog tests for skipping

These tests appear to be sensitive to machine-epsilon level
perturbations in linear system solution.

The issue disappears by changing "(1.0/temp) * y" to "y/temp" in
superlu/dpivotL.c, or just by adding a Newton refinement to
_linprog_ip._sym_solve:

     dr = r - matvec(v)
     dv = solve(dr)
     v = v + dv

However, the problem is probably not the linear system solution itself,
but in what makes the test this sensitive to perturbations.

tylerjereddy/scipy,scipy/scipy,Stefan-Endres/scipy,arokem/scipy,mdhaber/scipy,perimosocordiae/scipy,tylerjereddy/scipy,ilayn/scipy,ilayn/scipy,zerothi/scipy,anntzer/scipy,Stefan-Endres/scipy,arokem/scipy,pizzathief/scipy,endolith/scipy,matthew-brett/scipy,nmayorov/scipy,WarrenWeckesser/scipy,nmayorov/scipy,mdhaber/scipy,vigna/scipy,arokem/scipy,scipy/scipy,e-q/scipy,grlee77/scipy,perimosocordiae/scipy,rgommers/scipy,vigna/scipy,ilayn/scipy,matthew-brett/scipy,endolith/scipy,rgommers/scipy,nmayorov/scipy,perimosocordiae/scipy,nmayorov/scipy,tylerjereddy/scipy,anntzer/scipy,person142/scipy,perimosocordiae/scipy,grlee77/scipy,Eric89GXL/scipy,pizzathief/scipy,matthew-brett/scipy,andyfaff/scipy,vigna/scipy,andyfaff/scipy,pizzathief/scipy,WarrenWeckesser/scipy,Eric89GXL/scipy,rgommers/scipy,andyfaff/scipy,Stefan-Endres/scipy,Stefan-Endres/scipy,anntzer/scipy,scipy/scipy,aeklant/scipy,pizzathief/scipy,arokem/scipy,person142/scipy,mdhaber/scipy,scipy/scipy,person142/scipy,Eric89GXL/scipy,e-q/scipy,endolith/scipy,scipy/scipy,ilayn/scipy,aeklant/scipy,Stefan-Endres/scipy,rgommers/scipy,endolith/scipy,zerothi/scipy,ilayn/scipy,perimosocordiae/scipy,person142/scipy,anntzer/scipy,endolith/scipy,perimosocordiae/scipy,ilayn/scipy,aeklant/scipy,mdhaber/scipy,vigna/scipy,grlee77/scipy,pizzathief/scipy,anntzer/scipy,tylerjereddy/scipy,grlee77/scipy,Eric89GXL/scipy,e-q/scipy,zerothi/scipy,zerothi/scipy,andyfaff/scipy,WarrenWeckesser/scipy,andyfaff/scipy,mdhaber/scipy,aeklant/scipy,arokem/scipy,zerothi/scipy,nmayorov/scipy,mdhaber/scipy,rgommers/scipy,e-q/scipy,Eric89GXL/scipy,anntzer/scipy,andyfaff/scipy,e-q/scipy,Eric89GXL/scipy,person142/scipy,aeklant/scipy,tylerjereddy/scipy,matthew-brett/scipy,zerothi/scipy,grlee77/scipy,WarrenWeckesser/scipy,endolith/scipy,WarrenWeckesser/scipy,matthew-brett/scipy,scipy/scipy,Stefan-Endres/scipy,WarrenWeckesser/scipy,vigna/scipy