Comparing log configuration values do not correctly compare null values

During the boot of the logging subsystem values from the configuration are compared against the values from the model to determine if a change to the configuration is needed. When getting the configuration value it is wrapped with a String.valueOf() which for null values returns "null". This fails the comparison and results in the configuration being overwritten. For something like a handler this means log messages could be lost if rotate-on-boot is set to true or append is set to false.