o-full: declare a MariaDB mirror

MariaDB primary repository uses to fail this way:

http://yum.mariadb.org/5.5/rhel6-amd64/rpms/MariaDB-Galera-5.5.34-centos6-x86_64-server.rpm:
[Errno 12] Timeout on
http://yum.mariadb.org/5.5/rhel6-amd64/rpms/MariaDB-Galera-5.5.34-centos6-x86_64-server.rpm:
(28, 'Operation too slow. Less than 1 bytes/sec transfered the last 30
seconds')
o-full: install MySQL-python on RHEL
o-full: install qemu-kvm-rhev on RHEL

qemu-kvm-rhev provides a qemu-kvm-rhev that supersedes the standard
qemu-kvm. This package is not yet available in CentOS. So we have to
take care of that.
o-full: reactive rhel-x86_64-server-6-ost-4

rhel-x86_64-server-6-ost-4 can now be used again. Let's reenable it.
o-full: install rabbitmq-server like the other rpm
o-full: call yum to time in a row

yum may fail silently by eturning 0 even in a package is not
installed.
calling it two time in row in a hack that reduce a lot the number
of unexpected failure.
o-full: ensure yum did the job properly

yum may silently skip some package installation. We check everything
is here as expected.
puppet: ensure RHN channel is enabled for cloud-init