(2.11) Make disk.name and disk.uuid available in bdev

(2.11) Make disk.name and disk.uuid available in bdev

Until now Disk name and uuid was not available on bdev level.
In case of ExtStorage, this info is useful, and may be for other
templates in the future too.

This patch treats the name and uuid object slots just like the size
one and passes them to BlockDev.__init__() and to BlockDev.Create().

The ExtStrorage interface exports these options to scripts via the
VOL_CNAME and VOL_UUID environment variables.

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>
Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Klaus Aehlig <aehlig@google.com>

This should be backported since in stable-2.11 bdev.py is split
in lib/storage/*.

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>