Fix broken links to Log config files (#378)

This fixes the broken links to log configuration files, which were
pointing to the files that existed prior to 2.1. This clarifies the new
behavior since 2.1, and also provides the old names for reference.
diff --git a/_docs-2/configuration/files.md b/_docs-2/configuration/files.md
index 37aaa70..a6402ba 100644
--- a/_docs-2/configuration/files.md
+++ b/_docs-2/configuration/files.md
@@ -36,18 +36,15 @@
 
 ## Log configuration files
 
-### log4j-service.properties
+### log4j2-service.properties
 
-The {% ghc assemble/conf/log4j-service.properties %} file configures logging for most Accumulo services
-(i.e [Manager], [Tablet Server], [Garbage Collector]) except for the Monitor.
+Since 2.1, the {% ghc assemble/conf/log4j2-service.properties %} file configures logging for most Accumulo services
+(i.e [Manager], [Tablet Server], [Garbage Collector], [Monitor]). Prior to 2.1 this file was named `log4j-service.properties`
+and did not apply to the [Monitor] which was configured in a separate `log4j-monitor.properties`.
 
-### log4j-monitor.properties
+### log4j2.properties
 
-The {% ghc assemble/conf/log4j-monitor.properties %} file configures logging for the [Monitor].
-
-### log4j.properties
-
-The {% ghc assemble/conf/log4j.properties %} file configures logging for Accumulo commands (i.e `accumulo init`,
+The {% ghc assemble/conf/log4j2.properties %} file configures logging for Accumulo commands (i.e `accumulo init`,
 `accumulo shell`, etc).
 
 ## cluster.yaml