openstack-common: Using puppet from RHN

When installing puppet on Redhat, we shall take it from their
repositories and not from puppetlabs.

As of, setup_puppet_rpm() is only used by Centos so let's move the code
inside the Centos case.

Redhat only have to setup its repository and install the package.
puppet-master: ensure puppet can reach mysql DB
indent: drop some \t