When first initializing Review Board, we'd make use of default logging

settings, which weren't necessarily based on stored configuration. This

initialization happened prior to loading the site configuration, with

the expectation that on the first request, we'd load again and then

reload logging settings. However, this leaves a window of time in which

incorrect settings may be applied.
The reason we didn't always unconditionally reload logging settings is

that it could be a bit slow or disruptive. The proper tradeoff, which is

implemented in this change, is to compare settings and determine whether

a reload is required.
load_site_config() now stores the original version of the logging

settings (from the Django settings, which the logging configuration

pulls from) and compares them once settings are applied. If there were

any changes, it will force a logging restart.
The middleware that tries to handle all this on the first request no

longer tells load_site_config() to do a full-reload of settings. In

reality, this only ever forced a logging restart, and was a bit of a

hack to begin with, and led to spurious log messages about loading

logging settings when new threads started up.

Tested the initial initialize() and verified that the logging

settings had taken effect.
Tested load_site_config() with and without changes to logging

settings. Verified it only reloaded logging when there was a

difference.