Commit b7b13588 made it possible that the kinematic code could be
restarted after a flush_step_generation() call without a sufficient
delay.
Rename last_sg_flush_time to min_restart_time and use that to ensure
_calc_print_time() always pauses kin_flush_delay time since the last
flush_step_generation() call.
Also, update force_move to invoke flush_step_generation() after any
movements. This is needed to ensure there is a sufficient delay
should force_move be called on a stepper motor that is part of the
toolhead kinematics and is using a step generation "scan time".
This fixes possible "internal error in stepcompress" reports when
using FORCE_MOVE.
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
3d3b87f97f