This looks at both the file system and the database for new agent plugins.
If an agent plugin is different in the database than on the filesystem,
this scanner will stream the plugin's content to the filesystem. This
allows for the normal file system scanning to occur (the normal file
system scanning processor will see the new plugin from the database
now in the file system and will process it normally, as if someone
hand-copied that plugin to the file system). So the job of this scanner
is merely to look at the database and reconcile the file system so
the file system has the most up-to-date plugins. Any old plugins
will be deleted from the file system. This will delegate to
ProductPluginDeployer to do the actual deployment of agent plugins.