Issue #2241: use the WORKDIR directive

instead of an explicit 'cd' in the RUN declarations.

otobo.nginx.dockerfile

@@ -27,15 +27,14 @@ RUN apt-get update\
         libkrb5-dev \
         wget
 
+WORKDIR /usr/src
 RUN set -x && \
-    cd /usr/src \
     NGINX_VERSION="$( nginx -v 2>&1 | awk -F/ '{print $2}' )" && \
     NGINX_CONFIG="$( nginx -V 2>&1 | sed -n -e 's/^.*arguments: //p' )" && \
     wget "http://nginx.org/download/nginx-${NGINX_VERSION}.tar.gz" -O nginx.tar.gz && \
     wget https://github.com/stnoonan/spnego-http-auth-nginx-module/archive/${SPNEGO_AUTH_COMMIT_ID}.tar.gz -O spnego-http-auth.tar.gz
 
-RUN cd /usr/src && \
-    NGINX_CONFIG="$( nginx -V 2>&1 | sed -n -e 's/^.*arguments: //p' )" && \
+RUN NGINX_CONFIG="$( nginx -V 2>&1 | sed -n -e 's/^.*arguments: //p' )" && \
     tar -xzC /usr/src -f nginx.tar.gz && \
     tar -xzvf spnego-http-auth.tar.gz && \
     SPNEGO_AUTH_DIR="$( pwd )/spnego-http-auth-nginx-module-${SPNEGO_AUTH_COMMIT_ID_FILE}" && \