change mkdir in elasticsearch.Debian init script to take in account when DATA_DIR, LOG_DIR and/or WORK_DIR is an empty variable

Author: sp-joseluis-ledesma

templates/etc/init.d/elasticsearch.Debian.erb

@@ -149,7 +149,9 @@ case "$1" in
 	fi
 
 	# Prepare environment
-	mkdir -p "$LOG_DIR" "$DATA_DIR" "$WORK_DIR" && chown "$ES_USER":"$ES_GROUP" "$LOG_DIR" "$DATA_DIR" "$WORK_DIR"
+	for DIR in "$DATA_DIR" "$LOG_DIR" "$WORK_DIR"; do
+		[ ! -z "$DIR" ] && mkdir -p "$DIR" && chown "$ES_USER":"$ES_GROUP" "$DIR"
+	done
 	touch "$PID_FILE" && chown "$ES_USER":"$ES_GROUP" "$PID_FILE"
 
 	if [ -n "$MAX_OPEN_FILES" ]; then