[Gmsh] Avoiding duplicate surfaces with OpenCASCADE kernel

[Ingraham, Daniel J. (GRC-LTV0)]

> PS : as a workaround you can add
> 
> BooleanFragments{ Volume{:}; Delete; }{}
> 
> at the end of the file, which will make everything conformal... but it's expensive.
> 

Great! This fixes the issue in the simple example I posted. I'll give it
a try on the actual geometry I'm working with.

Thanks so much for your help!

Daniel