Upgrade Bash

Updated Dockerfile in order to update/upgrade bash to fix the security bug found by Red Hat https://securityblog.redhat.com/2014/09/24/bash-specially-crafted-environment-variables-code-injection-attack/

Dockerfile

@@ -6,7 +6,7 @@ RUN echo "deb http://ppa.launchpad.net/nginx/stable/ubuntu trusty main" > /etc/a
 RUN echo "deb-src http://ppa.launchpad.net/nginx/stable/ubuntu trusty main" >> /etc/apt/sources.list.d/nginx-stable-trusty.list
 RUN apt-key adv --keyserver keyserver.ubuntu.com --recv-keys C300EE8C
 RUN apt-get update
-RUN apt-get upgrade
+RUN apt-get install --only-upgrade bash
 RUN apt-get install -y  wget nginx
 
 RUN echo "daemon off;" >> /etc/nginx/nginx.conf