Update Akka configuration

Configures default logging levels, disables framework exit on fatal
error (harness should do it) and disables JVM shutdown hooks (benchmark
should handle it).

benchmarks/actors-akka/src/main/resources/reference.conf

@@ -2,14 +2,23 @@
 
 akka {
 
-  # Log level used by the configured loggers (see "loggers") as soon
-  # as they have been started; before that, see "stdout-loglevel"
-  # Options: OFF, ERROR, WARNING, INFO, DEBUG
-  loglevel = "WARNING"
-
-  # Log level for the very basic logger activated during ActorSystem startup.
+  # Log level for the very basic logger activated during startup.
   # This logger prints the log messages to stdout (System.out).
   # Options: OFF, ERROR, WARNING, INFO, DEBUG
   stdout-loglevel = "WARNING"
 
+  # Log level used by the configured loggers (see "loggers") as soon
+  # as they have been started; before that, see "stdout-loglevel".
+  loglevel = "WARNING"
+
+  # Log complete configuration upon start. Enable for debugging.
+  log-config-on-start = off
+
+  # Do not exit directly from the framework, let the higher-ups do it.
+  jvm-exit-on-fatal-error = off
+
+  # Do not install JVM shutdown hooks to terminate the ActorSystem.
+  # The benchmark should do it in its tear down stage.
+  jvm-shutdown-hooks = off
+
 }