Dont copy our metadata EA in copyfile()

Dont copy our metadata EA in copyfile()

Apparently Apple is now relying more on the AFP copyfile function
for file copies where source and destination are on the same vol.
The copying is done by our copyfile() function. It calls into
our VFS stack where in the end _all_ extended attributes of the
file, including our metadata EA, will be copied from source to
dest.
This resulted in an incorrect metadata EA on the destination file,
eg the CNID was still the one of the source file.
Obviously the metadata EA of the destination file must be created
such that all relevant fields are properly assigned.

Fixes bug #452.