Add information on --restart

We need to recommend that users use Systemd unit files if they want
the container to restart automatically.

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

cmd/podman/create.go

@@ -412,6 +412,10 @@ func parseCreateOpts(ctx context.Context, c *cli.Context, runtime *libpod.Runtim
 		blkioWeight                                              uint16
 		namespaces                                               map[string]string
 	)
+	if c.IsSet("restart") {
+		return nil, errors.Errorf("--restart option is not supported.\nUse systemd unit files for restarting containers")
+	}
+
 	idmappings, err := util.ParseIDMapping(c.StringSlice("uidmap"), c.StringSlice("gidmap"), c.String("subuidname"), c.String("subgidname"))
 	if err != nil {
 		return nil, err