[xen-tools-discuss] Update postinstall for CentOS 5

[Miguel Filho]

Hi all,
I've checked the postinstall.sh script for CentOS 5, it seems the code
that adds repositories in yum.conf is not needed. The package
centos-release creates the file CentOS-Base.repo inside
/etc/yum.repos.d, with almost the same content plus more stuff. So yum
ends up claiming about duplicated repositories.

I would like to suggest the removal of that procedure, since it's not needed.

Patch attached.

Regards,

Miguel