emulators/linux_base-c6: Use a CVE-free version of bash

Bash 4.1.2 as shipped with this Linux base port is vulnerable to
CVE-2014-6271 and CVE-2014-7169. As EL6 policy is to backport security
patches, use a RPM that is not vulnerable to either remote code execution
vulnerability.

While here:

• Add the proper UDPATES Master site
• remove sample files installation from Makefile, in favor of @sample

Approved by: swills (mentor)
Security: 71ad81da-4414-11e4-a33e-3c970e169bc2