enable debug logging

Author: mark-vieira

distribution/tools/server-cli/src/main/java/org/elasticsearch/server/cli/APMJvmOptions.java

@@ -75,7 +75,7 @@ class APMJvmOptions {
 
         // Logging configuration. Unless you need detailed logs about what the APM
         // is doing, leave this value alone.
-        "log_level", "warn",
+        "log_level", "debug",
         "log_format_file", "JSON",
         "application_packages", "org.elasticsearch,org.apache.lucene",
         "metrics_interval", "120s",