Use config_export function instead of calling dokku as a subcommand

plugins/config/commands

@@ -89,9 +89,9 @@ case "$1" in
   config)
     parse_config_args "$@"
     config_create
+    is_config_export "$@" && config_export "$DOKKU_CONFIG_TYPE" "$APP" && exit 0
 
     [[ "$APP" ]] && DOKKU_CONFIG_TYPE=$APP
-    [[ ! -s $ENV_FILE ]] && is_config_export "$@" && exit 0
     [[ ! -s $ENV_FILE ]] && echo "no config vars for $DOKKU_CONFIG_TYPE" && exit 1
 
     VARS=$(grep -Eo "export ([a-zA-Z_][a-zA-Z0-9_]*=.*)" $ENV_FILE | cut -d" " -f2-)
@@ -101,10 +101,6 @@ case "$1" in
         echo $VARS
         exit 0
       fi
-      if [[ "$var" == "--export" ]]; then
-        echo "$VARS" | awk '{print "export " $0}'
-        exit 0
-      fi
     done