remove duplicate default nginx config

Dockerfile

@@ -51,8 +51,7 @@ find /etc/php5/cli/conf.d/ -name "*.ini" -exec sed -i -re 's/^(\s*)#(.*)/\1;\2/g
 
 # nginx site conf
 RUN rm -Rf /etc/nginx/conf.d/* && \
-mkdir -p /etc/nginx/sites-available/ && \
-mkdir -p /etc/nginx/sites-enabled/ && \
+rm -Rf /etc/nginx/sites-available/default && \
 mkdir -p /etc/nginx/ssl/
 ADD ./nginx-site.conf /etc/nginx/sites-available/default.conf
 RUN ln -s /etc/nginx/sites-available/default.conf /etc/nginx/sites-enabled/default.conf