CA-46955: make code robust to parallel deletions of VBDs
CA-46955: make code robust to parallel deletions of VBDs

In general we should be very careful in code like this not to expect the configuration of "other VMs" to remain static while we run. In this case a parallel thread deleted a VBD which it "owned" and this cross-talk killed this thread.

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

johnelse/xcp-rrdd,simonjbeaumont/xcp-rrdd,sharady/xcp-networkd,koushikcgit/xcp-rrdd,johnelse/xcp-rrdd,koushikcgit/xcp-rrdd,djs55/xcp-networkd,sharady/xcp-networkd,djs55/xcp-networkd,koushikcgit/xcp-networkd,djs55/xcp-rrdd,koushikcgit/xcp-networkd,simonjbeaumont/xcp-rrdd,robhoes/squeezed,djs55/squeezed,koushikcgit/xcp-rrdd,djs55/xcp-rrdd