Adds a unit test to make sure the status endpoint doesn't ever show anything

with "token" in the name.

command/agent/agent_endpoint_test.go

@@ -1,6 +1,7 @@
 package agent
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
 	"io"
@@ -117,6 +118,15 @@ func TestHTTPAgentSelf(t *testing.T) {
 	if val.Coord != nil {
 		t.Fatalf("should have been nil: %v", val.Coord)
 	}
+
+	// Make sure there's nothing called "token" that's leaked.
+	raw, err := srv.marshalJSON(req, obj)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	if bytes.Contains(bytes.ToLower(raw), []byte("token")) {
+		t.Fatalf("bad: %s", raw)
+	}
 }
 
 func TestHTTPAgentReload(t *testing.T) {