There are a few classes that directly rely on log4j to be on the classpath instead and don't use the slf4j logging facade. This creates problems when trying to switch the logging implementation.
I don't know the impact of this change, but shouldn't this call `org.apache.solr.logging.MDCLoggingContext.clear()` ?
2. org.apache.solr.handler.component.RangeFacetProcessor and org.apache.solr.handler.component.RangeFacetRequest
should use slf4j instead of log4j
I had a stab at it at