Should fix
```
api/types/volume/volume_create.go
Line 10: warning: comment on exported type VolumeCreateBody should be of the form "VolumeCreateBody ..." (with optional leading article) (golint)
api/types/volume/volume_list.go
Line 12: warning: comment on exported type VolumeListOKBody should be of the form "VolumeListOKBody ..." (with optional leading article) (golint)
```
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Modify the service update and create APIs to return optional warning
messages as part of the response. Populate these messages with an
informative reason when digest resolution fails.
This is a small API change, but significantly improves the UX. The user
can now get immediate feedback when they've specified a nonexistent
image or unreachable registry.
Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
