Flux Index Bugs

[ajnonaka]

Thanks to Changho for spotting both of these.

Fixed a bug in the z ChiX stencil.

Fixed an error in the z heat flux indexing which doesn't ultimately affect the simulation since it's summed into the same location in memory in the end anyway regression tests will likely change when this is merged.

[isriva]

good catches! there is a small modification I would suggest in line 1364 above. but apart from that looks good to me!
interesting this was never caught -- I think this is because we only did equilibrium tests in z-direction (which would likely not be affected by this), whereas all nonequilibrium simulations were done by applying a gradient in x- and y- directions.

[ajnonaka]

What line 1364 modification are you suggesting? @isriva

[isriva]

@ajnonaka line 1364 of flucStag.cpp should be:
Real ChiX = 0.5*(chi(i,j,k-1,ns)*prim(i,j,k-1,6+nspecies+ns)+chi(i,j,k,ns)*prim(i,j,k,6+nspecies+ns));

[ajnonaka]

@isriva fixed!