JmxConfigurator logging improvements

JmxConfigurator is overly verbose about logging some things, and doesn't log enough in other cases.

• unregisterChannel does not have an equivalent for registerChannel(..., register_protocols=false)
  It will log a WARN message for each protocol if the channel was registered with register_protocols=false
• several places log an exception at ERROR level then throw it.
  If the exception is being thrown, it generally should not be logged above DEBUG
• a few spots catch and log an exception message but do not throw it
  These should also log the full stack trace at DEBUG