core: correct ProcessOvfUpdateForStorageDomainCommand lock properties

ProcessOvfUpdateForStorageDomainCommand lock is released always on the
execute phase prior to change I54cc929937d3b14dc49a2edab9e763cbe603a9c3
- either by the child command or because the created tasks aren't added
to the command task
list.

This patch changes the applyLockProperties method to state that
explictly.

Change-Id: I938e8a0ce74bb931635948210f26a1f451fbe815
Signed-off-by: Liron Aravot <laravot@redhat.com>