Speed blocks break instantly when running on top of them

[falkreon]

This is technically intentional behavior, but it exists as a temporary solution to a problem:

• When a speed block is hit above the threshold speed, it disappears clientside
• The server doesn't care about this. The server can, in due time, notice the same thing and disappear.
• However, the server cares about falling through solid blocks.
• The result is janky fallthrough behavior

Potentially the fix is only breaking the blocks serverside, but this needs more research and testing.