How to reproduce:
1. Create new project file
2. Add a new 3D GameObject in Hierarchy Window
3. Add Cloth component
4. Drag GameObject to Project folder to make it a prefab
5. Select GameObject in the Hierarchy Window and repeatedly hit 'Apply' in Inspector

Actual result: Hitting 'Apply' on a prefab with cloth collider creates multiple mesh collider components

Reproduced with: 2017.3.0f3, 2018.1.0b1
Not reproduced with: 2017.2.1p1

Regression since: 2017.3.0a7