Before this commit, the oarsub command:
oarsub -r"2018-01-01 00:00:00" -t noop -l {type='disk'}/disk=1
gives all 1st disks of the cluster when we expect only one disk.

To obtain only one disk, we need to have unique values for property
disk (which was not the case before this commit, see bug 8260).

This commit changes disk property from 1..k (i for disk number i) on
each node, to device_uid.node_uid (ex: sda.grimoire-1) which is unique.