The set hidden attribute ioctl doesn't work for
~/Documents/.Sugar-Metadata, however it is not necessary to apply the
flag, since it is a Linux file system. This patch checks to see if the
destination of the copy is ~/Documents, and if so, skips the ioctl.

Fixes #4656
Merge branch 'copydocuments' of git://github.com/walterbender/sugar into walterbender-copydocuments