Fix wp 4.9 install

The admin setup page sends an email anyway and sendmail barfs
with some /var/spool/xx being rofs

Dockerfile

@@ -48,6 +48,9 @@ RUN crudini --set /etc/php/7.0/apache2/php.ini PHP upload_max_filesize 500M && \
     crudini --set /etc/php/7.0/apache2/php.ini Session session.gc_probability 1 && \
     crudini --set /etc/php/7.0/apache2/php.ini Session session.gc_divisor 100
 
+# Hack to stop sendmail/postfix to keep retrying sending emails because of rofs
+RUN rm -rf /var/spool
+
 ADD start.sh cron.sh /app/code/
 
 CMD [ "/app/code/start.sh" ]