core: fix NPE on failure to run stateless vm

Running VM in stateless mode is composed of two parts: the stateless
snapshot creation and then running the VM. In the second part we invoke
RunVmCommand and ask it to end the operation's job when it is done.

The problem was that RunVmCommand didn't get the operation's job, so
when it tried to end the job, NPE was thrown and the job's tasks
remained unfinished. This problem is solved by passing the operation's
job to the inner RunVmCommand.

Change-Id: I922b0cfaf9a50de35ec9c2ca6195d5326600ce5a
Bug-Url: https://bugzilla.redhat.com/1039507
Signed-off-by: Arik Hadas <ahadas@redhat.com>