Improve stability of ContinuationIsExact tests
The default nstlist value in tests is set to 8. This is appropriate for
NormalIntegrators/MdrunNoAppendContinuationIsExact
tests, which do the
restart after 8 steps, so the "full" trajectory and the "restarted"
trajectory update their lists at the same time. However, pairlist tuning
often increases the nstlist
value, which might affect the "full" run.
Here, we force the nstlist
to be half the nsteps
for the "full" run by
setting it via CLI option.