Fix example of relative WORKDIR

Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
Update libcontainer to 68ea1234a0b046803aacb2562df

Signed-off-by: Michael Crosby <michael@docker.com>
Ensure thread is locked in sysinit for docker

Signed-off-by: Michael Crosby <michael@docker.com>
Purge the bits of pkg/system that moved to libcontainer/system

Signed-off-by: Andrew Page <admwiggin@gmail.com>
Docker RunIn support phase 1

Docker-DCO-1.1-Signed-off-by: Vishnu Kannan <vishnuk@google.com> (github: vishh)
Implement the core of runin support in docker.

Docker-DCO-1.1-Signed-off-by: Vishnu Kannan <vishnuk@google.com> (github: vishh)
Adding Remote API for runin.

Docker-DCO-1.1-Signed-off-by: Vishnu Kannan <vishnuk@google.com> (github: vishh)
Added client CLI for runin.

Docker-DCO-1.1-Signed-off-by: Vishnu Kannan <vishnuk@google.com> (github: vishh)
'docker runin' works.

TODO:
Implement a way to track commands being run in a container to stop them on-demand (daemon mode) and when the container exits.

Docker-DCO-1.1-Signed-off-by: Vishnu Kannan <vishnuk@google.com> (github: vishh)
Renamed 'runin' to 'exec' in the API and the implementation.

Docker-DCO-1.1-Signed-off-by: Vishnu Kannan <vishnuk@google.com> (github: vishh)