CA-28958: fix a VBD create/destroy race in the VBD.device 'autodetect' choosing logic.
CA-28958: fix a VBD create/destroy race in the VBD.device 'autodetect' choosing logic.

A parallel VBD.destroy can come in and delete a VBD just before we attempt to look up the device field. Obviously it doesn't matter what device this VBD was since it has just been deleted... so just ignore it.

Signed-off-by: David Scott <63c9eb0ea83039690fefa11afe17873ba8278a56@eu.citrix.com>

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