GroovyScriptFactory should use BeanClassLoader instead of default class loader

As GroovyScriptExecutingMessageProcessor creates new instances of GroovyScriptFactory without calling setBeanClassLoader() and setBeanFactory() Groovy scripts are loaded with the default class loader (ClassUtils.getDefaultClassLoader()) instead of the BeanClassLoader.

This results in ClassNotFoundExceptions if Groovy classes are referenced that are available on BeanClassLoader but not on the default class loader (e.g. the current thread's ContextClassLoader)