Add a yum upgrade to CentOS65

This patch adds a 'yum upgrade' to base.sh to ensure we have the latest
packages for each build.  The key driver for this at this time is the
shellshock bash bug, but should simplifiy things for future patching.

Fixes: DHC-2458
Merge pull request #13 from drwahl/master

Add a yum upgrade to CentOS65