prevent plugin volume to have ownerships overwritten by docker

srcs/requirements/wordpress/Dockerfile

@@ -26,9 +26,17 @@ RUN rm -rf /var/lib/apt/lists/*
 COPY ./conf/www.conf /etc/php7/php-fpm.d/
 RUN mkdir /run/php/
 
+ARG WP_VOLUME_DIR
+ARG WP_VOLUME_PLUGINS
 ARG SERVER_MAX_UPLOAD_SIZE
 ARG SERVER_EXECUTION_TIME
 
+# IS IT USEFUL ?
+# # create and empty volumes dir
+# RUN mkdir -p ${WP_VOLUME_DIR}   ${WP_VOLUME_PLUGINS}   && \
+# 	rm -rf     ${WP_VOLUME_DIR}/* ${WP_VOLUME_PLUGINS}/*
+
+
 # replace max file size upload and execution time
 RUN sed -i "s/\(upload_max_filesize = \).*\(M\)/\1${SERVER_MAX_UPLOAD_SIZE}\2/g" /etc/php7/php.ini && \
 	sed -i "s/\(post_max_size = \).*\(M\)/\1${SERVER_MAX_UPLOAD_SIZE}\2/g" /etc/php7/php.ini && \