Comment 1 for bug 1810927

Reviewed: https://review.openstack.org/629152
Committed: https://git.openstack.org/cgit/openstack/os-win/commit/?id=593152d8d8b34a17beed3226fef40275fb4e15dd
Submitter: Zuul
Branch: master

commit 593152d8d8b34a17beed3226fef40275fb4e15dd
Author: Lucian Petrut <email address hidden>
Date: Tue Jan 8 13:21:21 2019 +0200

    Silently continue when disconnecting missing vhds

    os-win should silently pass when requested to disconnect a vhd that's missing.
    At the moment, it's erroring out, which prevents some Nova instances from being
    cleaned up.

    This change checks if the image to be disconnected actually exists before
    attempting to open it.

    Change-Id: Ic734d38e1939165a89a79842d37e98b4cbbcb3bf
    Closes-Bug: #1810927