This patch removes a script with SUID flag,restart_docker_container,
which was used to restart docker containers and replaces it by
native python implementation. The aim of this replacmenet is to reduce
the security risk caused by SUID binaries, as well as to implement
more features and unit test coverages easily.
To allow swift user to manage docker conainers, now it is required
that swift user belong to docker group and have access to docker
unix domain socket.
Change-Id: I8103d4d826f5121e16f67f1ff49102ceecaf8a80