cmd/containerboot: fix TS_STATE_DIR environment variable

It's supposed to set `--statedir` rather than `--state` file.

Fixes #6634.

Signed-off-by: Anton Tolchanov <anton@tailscale.com>
(cherry picked from commit 5ff946a9e6)

cmd/containerboot/main.go

@@ -275,7 +275,7 @@ func tailscaledArgs(cfg *settings) []string {
 	case cfg.InKubernetes && cfg.KubeSecret != "":
 		args = append(args, "--state=kube:"+cfg.KubeSecret, "--statedir=/tmp")
 	case cfg.StateDir != "":
-		args = append(args, "--state="+cfg.StateDir)
+		args = append(args, "--statedir="+cfg.StateDir)
 	default:
 		args = append(args, "--state=mem:", "--statedir=/tmp")
 	}

cmd/containerboot/main_test.go

@@ -146,7 +146,7 @@ func TestContainerBoot(t *testing.T) {
 				"TS_STATE_DIR": filepath.Join(d, "tmp"),
 			},
 			WantArgs1: []string{
-				"/usr/bin/tailscaled --socket=/tmp/tailscaled.sock --state=/tmp --tun=userspace-networking",
+				"/usr/bin/tailscaled --socket=/tmp/tailscaled.sock --statedir=/tmp --tun=userspace-networking",
 				"/usr/bin/tailscale --socket=/tmp/tailscaled.sock up --accept-dns=false --authkey=tskey-key",
 			},
 			Status1: ipnstate.Status{