Disable cos acceleration for non leap-frog code paths

Disable cos acceleration for non leap-frog code paths

The cos acceleration is only applied in leap-frog. grompp and mdrun
would, however, happily accept non-zero cos-accel input, and report
viscosity-related quantities without ever applying the acceleration
for all other integrators.

This change adds a check at grompp time (to avoid new tprs with
non-implemented parameter combinations being created), and at
runner time (to catch older tprs). Should probably be backported
to the supported releases.

Refs #3903