Description of problem:

When the user clicks on ChangeCD on the UI for a CD stored on a block data domain, there are 2 problems:

1. VDSM does not activate the LV containing the image, so the ChangeCD fails

2018-08-24 12:24:49,128+1000 INFO  (jsonrpc/0) [api.virt] FINISH changeCD return={'status': {'message': 'Drive image file could not be found', 'code': 13}} from=::ffff:192.168.122.253,51448, flow_id=45abefb9-cdea-4c14-9312-dbd4c214b299, vmId=f6e82d73-ccf9-48aa-9e38-2ee1473da9c8 (api:52)

2. If one boots a VM with the CD attached it activates the LV, but then after changing the CD (or ejecting it), the LV is still active. It should have been deactivated.

Version-Release number of selected component (if applicable):
vdsm-4.20.35-1.el7ev.x86_64

How reproducible:
100%

Steps to Reproduce:
1. Upload 2 ISOs do Data Domain
2. Boot VM with 1 ISO attached
3. ChangeCD to a CD to the other image (fail)
4. Manually activate the LV, try [3] again (suceeds)
3. Check the status of the LV of the initial CD that is not in use (active)

Actual results:
VDSM does not handle LV activation/deactivation on ChangeCD for ISOs uploaded to block data domains

Expected results:
LV activated on ChangeCD, and deactivated when image stops being used.