WFCORE-129 - overlay does not work for zipped files in exploded archive

WFLY: https://issues.jboss.org/browse/WFCORE-129
6.4.0: https://bugzilla.redhat.com/show_bug.cgi?id=1147352
That parent.isDirectory() check is the problematic bit that was not in the original code. Because parent get modified by the loop, parent.isDirectory will almost always be true, no matter how many directories need to be created (as parent always ends up as the top level directory, the loop above won't exit until parent.exists() is true.

If parent.isDirectory() is false at this point I think it is an error condition, as they are trying to mount an overlay under a physical file.