Fixes where mdrun could behave incorrectly

Fix incorrect LJ repulsion force switching on GPUs

When using a CUDA or OpenCL GPU, the coefficient for the second order term for the LJ repulsion in the force switching function, called ‘A’ in the manual, had the wrong sign. This lead to very small errors in the forces and the pressure. Note that the dispersion force switching was correct. Although the effect on individual atoms pairs was negligible, their combined effect on the pressure could lead to deformation of CHARMM membrane systems, where LJ force switching is regularly applied.

Issue 2845