Update Centos 6 release to 6.9

[staticfloat]

It'd be great to update the Centos 6 image to a base of 6.9.

[staticfloat]

I just confirmed that this was super easy to do with your Vagrant and scripts setup. Nice work! I've pushed my image to staticfloat/centos-i386:centos6, but of course, it'd be nice to have the canonical source up to date as well. :)

[staticfloat]

Ah, my image also contains this fix, which is important: #6