Bats make walking sounds when flying above stairs

Verification builds: Release_803004
Summary:
When bats are flying above stair blocks, they make human step sounds.

Impact:
It's illogical, can't use a lot of bats for particle-type stuff because they make sounds that shouldn't be there.

Repro Steps:
Create a world, make a small room with stairs on the ground and spawn a load of bats.

Observed Results:
Bats make walking sounds while flying around

Expected Results:
No sounds should be made

Video: https://drive.google.com/a/noxcrew.com/uc?id=1uWcwzYiOoUs5GsNundoWXjKQcesNECI2