Can't create node

Using LTS Jenkins ver. 1.532.1 installed by rpm on CentOS 6.4

jenkins_api_client.git on fa7a2ea

```ruby
ruby scripts/login_with_irb.rb

puts @client.job.list(".*")

puts @client.node.create_dump_slave(
  :name => "slave1",
  :slave_host => "10.10.10.10",
  :private_key_file => "/root/.ssh/id_rsa",
  :executors => 10,
  :labels => "slave, ruby"
)
```

```
ruby scripts/login_with_irb.rb
logged-in to the Jenkins API, use the '@client' variable to use the client
irb(main):001:0> puts @client.job.list(".*")
I, [2014-02-06T15:18:16.314955 #47425]  INFO -- : Obtaining jobs matching filter '.*'
I, [2014-02-06T15:18:16.315061 #47425]  INFO -- : GET /api/json
whoami
=> nil
irb(main):002:0> puts @client.node.create_dump_slave(
irb(main):003:1*   :name => "slave1",
irb(main):004:1*   :slave_host => "10.10.10.10",
irb(main):005:1*   :private_key_file => "/root/.ssh/id_rsa",
irb(main):006:1*   :executors => 10,
irb(main):007:1*   :labels => "slave, ruby"
irb(main):008:1> )
I, [2014-02-06T15:18:22.079072 #47425]  INFO -- : Creating a dump slave 'slave1'
I, [2014-02-06T15:18:22.079319 #47425]  INFO -- : GET /api/json
I, [2014-02-06T15:18:22.085380 #47425]  INFO -- : POST /computer/doCreateItem
E, [2014-02-06T15:18:22.099554 #47425] ERROR -- : JenkinsApi::Exceptions::InternalServerError: Internel Server Error. Perhaps the in-memory configuration Jenkins is different from the disk configuration. Please try to reload the configuration
JenkinsApi::Exceptions::InternalServerError: Internel Server Error. Perhaps the in-memory configuration Jenkins is different from the disk configuration. Please try to reload the configuration
	from /Users/loa/workspace/github/jenkins_api_client/lib/jenkins_api_client/client.rb:721:in `handle_exception'
	from /Users/loa/workspace/github/jenkins_api_client/lib/jenkins_api_client/client.rb:351:in `api_post_request'
	from /Users/loa/workspace/github/jenkins_api_client/lib/jenkins_api_client/node.rb:175:in `create_dump_slave'
	from (irb):2
irb(main):009:0>
```