CA-116958: "VM.copy locking failed" error observed on build - 75698

Override slave mode lvm.conf for lvchange --refresh command on slaves

Signed-off-by: Chandrikas Srinivasan <chandrika.srinivasan@citrix.com>
Acked-by: Germano Percossi <germano.percossi@citrix.com>

GitHub: closes #36 on xapi-project/sm