Download pluginu s curl

Dockerfile

 FROM graylog/graylog:3.1
 MAINTAINER Andrej Ramašeuski <andrej.ramaseuski@pirati.cz>
-RUN apt-get install wget && wget -O /usr/share/graylog/plugin/graylog-plugin-auth-sso-3.1.0.jar https://github.com/Graylog2/graylog-plugin-auth-sso/releases/download/3.0.0/graylog-plugin-auth-sso-3.1.0.jar
+RUN curl -OL -o graylog-plugin-auth-sso-3.1.0.jar https://github.com/Graylog2/graylog-plugin-auth-sso/releases/download/3.1.0/graylog-plugin-auth-sso-3.1.0.jar