This commit changes Ironic deploy ramdisk to find out
the virtual media device by using labels instead of
looking at the model of block device. This helps in
finding out the device irrespective of the hardware.
Corresponding Ironic change is
If5b78d9af7048f2631d050ee5ce01ab7a67e2354.
Closes-Bug: #1429340
Change-Id: I5e8a706989bad13051eb47db0b1e762e6c672318