Upgrading a JAR extension which contains new components produce warnings

During the upgrade, the extension manager tries to register the components of the new version, but the classloader has been reloaded yet so it cannot find the new corresponding classes and produce warnings like:

Can't find any existing component with class [org.xwiki.export.pdf.internal.macro.PdfTocTreeBuilderFactory]. Ignoring it.

The components are all reloaded and registered at the end of the full installation job if there is any upgrade or uninstall.