Update Dockerfile

Author: Álvaro Alonso

extras/docker/Dockerfile

@@ -15,9 +15,10 @@ RUN sudo apt-get update && \
 # Download latest version of the code and install npm dependencies
 RUN git clone https://github.com/ging/fiware-cloud-portal.git && \
 	cd fiware-cloud-portal && \
+	git checkout tags/5.4 && \
 	npm install && \
 	./node_modules/grunt-cli/bin/grunt
 
 # Run Cloud Portal
 WORKDIR /opt/fiware-cloud-portal
-CMD ["sudo", "node", "server.js"]
+CMD ["sudo", "node", "server.js"]