meta-tizen: Enable xattr in created images

meta-tizen: Enable xattr in created images

Adding the xattr in the rootfs before creating the image doesn't work
(xattr are not copied by "mkfs.ext3). The solution is to mount the
image after its creeation and then, set the xattr.

Note that it seems that adding the xattr in the rootfs before creating
the image seems to be needed. Without this step the xattr are not set,
even after setting them with this solution. I don't know why...

(From meta-tizen rev: a4ec39e3beeafbbc6269a4cd918be4a04e9a8a26)

Signed-off-by: Kévin THIERRY <kevin.thierry@open.eurogiciel.org>
Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>