Kernel's debug logging was found to be causing problems in very rare circumstances via an interaction with AccessManager.  As a workaround, the logging functionality was tied to the kernel.debug system property -- logging is only enabled if debug is on.

Unfortunately this has proved inadequate, as it can be difficult or impossible to ensure that the system property makes it to the particular VM where it is needed.  Therefore we need to add a registry key to control kernel debugging, much as with KernelDownloadUrl.