fix escaping

{{cookiecutter.packer_name}}/packer.json

@@ -33,10 +33,10 @@
       "ssh_username"  : "ubuntu",
       "instance_type" : "m3.medium",
     {% endraw -%}
-      "ami_name"      : "{{cookiecutter.packer_name}}-{{timestamp}}",
+      "ami_name"      : "{{cookiecutter.packer_name}}-{% raw -%}{{timestamp}}{% endraw -%}",
       "tags"          : {
 		  "role"       : "{{cookiecutter.packer_name}}",
-		  "build_date" : "{{timestamp}}"
+		  "build_date" : "{% raw -%}{{timestamp}}{% endraw -%}"
       }
     }
   ],