Black-142: Sentinel

In order to use Redis Sentinel, a few modification were required:
* Add logging attributes to the defaults and use them in the sentinel.conf
* Fix an ERB typo where it was missing the `=`
* Stop setting the current attributes back as normal attributes. This was causing me problems (likely because we use wrapper cookbooks vs. roles) and I don't see the benefit from it.
* And the biggie: Only every make the redis and sentinel conf files once, at first run. This allows Redis and Sentinel to rewrite their files using `CONFIG REWRITE` which is a major piece of Sentinel functionality. This means that a server that starts as a master but becomes a slave will reboot as a slave in the future.