Calls to isXXXEnabled translate to a call to Logger.callTurboFilters which invokes DuplicateMessageFilter with a null format

DuplicateMessageFilter usage of LRUMessageCache will group together all null formats under msgCount.

e.g.

msgCache.getMessageCount(null) = msgCount 1
msgCache.getMessageCount(null) = msgCount 2
msgCache.getMessageCount(null) = msgCount 3