[ofw] Add Assert to debug BS while deleting WDF device

[Hefty, Sean]

> The function that fails is WdfDeviceCreateSymbolicLink that returns
> STATUS_OBJECT_NAME_COLLISION (0xC0000035L). It doesn't happen consistently
> but it happens from time to time.

Does the following describe your testing?

1 Load the stack
2 Start opensm
3 Unload the stack
4 Reload the stack
5 Unload the stack
6 crash on unload

I'm wondering if Windows maintains the symbolic link (or is slow to destroy it) if an application actively using it when the kernel removes it.  If so, this would explain the failure to recreate it at step 4 above.  And if this is the case, then I'm not sure what a fix would be..

- Sean