The reexec package facilitates the busybox style reexec of the docker binary that we require because
of the forking limitations of using Go. Handlers can be registered with a name and the argv 0 of
the exec of the binary will be used to find and execute custom init paths.
Command returns *exec.Cmd which has Path as current binary.
For example if current binary is "docker" at "/usr/bin/", then cmd.Path will
be set to "/usr/bin/docker".