Prevent super long strides with new salk-steps commands initiated mid-stride

[thatrobotguy]

Branch: rbe-595
I sent a new walk steps (right foot first, 2 steps) command mid-stride and it started stretching its leg out really super far.
The new walk steps command should not make the robot get into a squatting position. We do not want Warner keeling over unless we till him to explicitly.
I think there should be a cap to how far the robot should extend its leg when starting a stride.