Remove yum update

Running yum update during building the image will cause inconsistent WildFly images to be built. I assume the Fedora docker image is updated on a regular basis any ways?

I've also seen several issues with this:

* https://bugzilla.redhat.com/show_bug.cgi?id=1101654
* The command [/bin/sh -c yum -y update] returned a non-zero code: 1 (output below)

---

Failed:
  iputils.x86_64 0:20121221-5.fc20       iputils.x86_64 0:20121221-6.fc20      
  systemd.x86_64 0:208-15.fc20           systemd.x86_64 0:208-16.fc20          

Complete!
2014/06/02 19:55:55 The command [/bin/sh -c yum -y update] returned a non-zero code: 1