CA-43021: Fix bug detecting the backing vhd file caused by reading the wrong device's minor number.
CA-43021: Fix bug detecting the backing vhd file caused by reading the wrong device's minor number.

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

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