attach/detach does not correctly set owner/neighbour

Summary

(exchange platform 1010) Issue: If statement does not check to see if face was modified in codeblock from lines 115 to 156 of attachInterface.C. This results in the attach instructions for the faces on the master patch being overwritten with old values for owner/neighbour/patchID.

The overall effect is that attachInterface.C:

deletes the faces from the slave patch as expected, but,
does not delete the faces from the master patch, and the cells across the faceZone are not attached. So the information in polymesh/<neighbour,boundary,owner> is incorrect

Adding a check to exclude faces that have been modified at line attachInterface.C:176 fixes this behaviour.

Possible fixes

attachInterface.C