Images may be created with a VOLUME stanza pointed to drive letters that
are not C:. Currently, an image that has such VOLUMEs defined, will
cause containerd to error out when starting a container.
This change skips copying existing contents to volumes that are not C:.
as an image can only hold files that are destined for the C: drive of a
container.
Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>