Fix wallcycle counting with md-vv, sd and sd2

Fix wallcycle counting with md-vv, sd and sd2

Previously the coordinate update for the first half of velocity Verlet
and (where applicable) the second half of the SD integrators was left
out of the walltime accounting, and showed up in the "Rest"
section. With this fix, the number of "update" steps reported depends
on exactly which flavour of which integrator is in use, because
there's also some number of calls to do constraining and/or energy
communication. Those numbers vary with either the flavour of
integrator, or the number of iterations MTTK actually needs.

Change-Id: Ib294455b7277caf89018c413d6c1c0ebf93c6ddb