Modify volume mounts SELinux labels on the fly based on :Z or :z

Looking for comment on this patch.  

The first patch should be able to be applied without any controversy.  The send patch is extending the qualifiers on the -v command to allow an admin to tell the system to relabel, content.  There might be a need for something similar for changing the DAC Permissions.
How about.

Labeling systems like SELinux require proper labels be placed on volume content
mounted into a container, otherwise the secuirty system might prevent the 
processes running inside the container from using the content.  By default, 
volumes are not relabeled. 

Two suffixes :z or :Z can be added to the volume mount.  These suffixes tell 
docker to relabel file objects on the shared volumes. The 'z' option tells 
docker that the volume content will be shared between containers.  Docker will 
label the content with a shared content label. Shared volumes labels allow all 
containers to read/write content.  The 'Z' option tells docker to label the 
content with a private unshared label. Private volumes can only be used by the 
current container.