Hyper-V:Preserve config drive image after the instance is resized

If we configure config_drive_cdrom=True in nova.conf,
the config drive image will be lost after the instance
is resized on hyperV. This is because nova compute will
not copy the disk file if the file's ResourceSubType
is not 'Virtual Hard Disk'.

This commit adds 'Virtual CD/DVD Disk' into disk_resources
to preserve the config drive image after the instance is
resized.

Closes-Bug: #1250324
(cherry-picked from commit 710cf4e3a7ee3b89e462ec5ff2291e1177556819)

Change-Id: Ia125a8b132d194ddc2230754fd1b813698b410a8