Added some code to prevent the static intialization block from triggering dynamic class discovery if the package manager is in the process of loading packages. Some packages with custom GenericPropertiesCreator.props files would cause the GenericPropertiesCreator class to be loaded (and thus the dynamic class discovery process to start) during the package loading process - if this occurred between package A and package B, when A depends on B, then class not found errors will occur (because B's classes would not have been injected into the classpath yet).

git-svn-id: https://svn.cms.waikato.ac.nz/svn/weka/trunk@9872 e0a1b77d-ad91-4216-81b1-defd5f83fa92
Merge remote-tracking branch 'upstream'