Docker: Use www-data instead of a new user for httpd

Dockerfile

@@ -4,8 +4,6 @@ COPY ./viewer /usr/local/apache2/htdocs/
 
 COPY ./docker/custom-httpd.conf /usr/local/apache2/conf/httpd.conf
 
-RUN adduser --disabled-password httpdusr
+RUN chown -R www-data /usr/local/apache2/logs
 
-RUN chown -R httpdusr /usr/local/apache2/logs
-
-USER httpdusr
+USER www-data