Add mention of mounting cgroupfs properly to PACKAGERS.md

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Merge branch 'master' of github.com:dotcloud/docker
Remove hard coding of SELinux labels on systems without proper selinux policy.

If a system is configured for SELinux but does not know about docker or
containers, then we want the transitions of the policy to work.  Hard coding
the labels causes docker to break on older Fedora and RHEL systems

Docker-DCO-1.1-Signed-off-by: Dan Walsh <dwalsh@redhat.com> (github: rhatdan)
In certain cases, setting the process label will not happen.

When the code attempts to set the ProcessLabel, it checks if SELinux Is
enabled.  We have seen a case with some of our patches where the code
is fooled by the container to think that SELinux is not enabled.  Calling
label.Init before setting up the rest of the container, tells the library that
SELinux is enabled and everything works fine.

Docker-DCO-1.1-Signed-off-by: Dan Walsh <dwalsh@redhat.com> (github: rhatdan)
Change ownership to root for ADD file/directory

Docker-DCO-1.1-Signed-off-by: Guillaume J. Charmes <guillaume@charmes.net> (github: creack)
docs: explain what docker run -a does

This adds a bit of documentation for the `-a` flag for docker run.

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
Merge pull request #3971 from creack/fix_add_ownership

Change ownership to root for ADD file/directory
Merge pull request #4953 from rhatdan/selinux

These two patches should fix problems we see with running docker in the wild.
Merge pull request #4972 from unclejack/document_a_flag

docs: explain what docker run -a does