`javaposse.jobdsl.plugin.GlobalJobDslSecurityConfiguration.xml` do include serialized category `GlobalConfigurationCategory$Security`.

As a result, on load a fresh new instance is created and `Security` is not a singleton anymore.

This introduced https://github.com/jenkinsci/configuration-as-code-plugin/issues/253

the root cause is groovy property syntax used to override hudson.model.Descriptor#getCategory, which appears as a persistent field from XStream point of view