Revert "Refactor SlaveInterface::calcSpeed"
This reverts commit 4e2a815b9a107663a3d75e9d9d1be336adea888e.
This commit causes crashes due to improper division and there are some
outstanding code review issues as well.
BUG: 402665
(cherry picked from commit b8a5f34b34b6c4e37684fe2782b8cf39c38cd928)