When XML resources are modified using an effective group because the setGID bit is set on the resource NativeBroker.defragXMLResource might throw a PermissionDeniedException.

With this patch applied, this can no longer happen as the call to DocumentImpl#copyOf is removed in defragXMLresource.
The temporary document is just a container to realign nodes on one BTree page and is destroyed within the method.

…Resource

Testing has shown that the previous call to construct tempDoc was actually the correct one,
as it is using the default file permissions of the pool.
That is key for situations in which the subject initiating the defragmentation is not the
_owner_ of the document and only belongs to the group with write permission.