Assing RABBITMQ_CONFIG_ARG_FILE variable

The rabbit_prelaunch module can read the os:getenv(RABBITMQ_CONFIG_ARG_FILE) correctly

Author: Gabriele

scripts/rabbitmq-server

@@ -187,6 +187,7 @@ RABBITMQ_PRELAUNCH_NODENAME="rabbitmqprelaunch${$}@localhost"
 NOTIFY_SOCKET= \
 RABBITMQ_CONFIG_FILE=$RABBITMQ_CONFIG_FILE \
 ERL_CRASH_DUMP=$ERL_CRASH_DUMP \
+RABBITMQ_CONFIG_ARG_FILE=$RABBITMQ_CONFIG_ARG_FILE \ 
 RABBITMQ_DIST_PORT=$RABBITMQ_DIST_PORT \
     ${ERL_DIR}erl -pa "$RABBITMQ_EBIN_ROOT" \
     -boot "${CLEAN_BOOT_FILE}" \