Add the rmi flag to podman-run to delete container image

The --rmi flag will delete the container image after its execution
unless that image is already been used by another container(s).

This is useful when one wants to execute a container once and remove
any resources attached to it.

Signed-off-by: Boaz Shuster <boaz.shuster.github@gmail.com>

pkg/spec/createconfig.go

@@ -156,6 +156,7 @@ type CreateConfig struct {
 	Resources         CreateResourceConfig
 	RestartPolicy     string
 	Rm                bool           //rm
+	Rmi               bool           //rmi
 	StopSignal        syscall.Signal // stop-signal
 	StopTimeout       uint           // stop-timeout
 	Systemd           bool
@@ -233,6 +234,10 @@ func (c *CreateConfig) createExitCommand(runtime *libpod.Runtime) ([]string, err
 		command = append(command, "--rm")
 	}
 
+	if c.Rmi {
+		command = append(command, "--rmi")
+	}
+
 	return command, nil
 }