CA-100685: When domain disappears during VM shutdown operation, just go ahead instead of rasing any cancellation error

Signed-off-by: Zheng Li <zheng.li@eu.citrix.com>
Merge pull request #1377 from akshayramani/Oliver/HFX-822

Oliver/HFX-822: CA-100685: When domain disappears during VM shutdown operation, just go ...