common: Adding generic mount_fs call

As we need to setup the same fs twice at least (one for base, one for
the others), let's make a generic mount_fs function to avoid code
duplication.

More than that a bug was part of the mounting iso semantic. Since we
umount everything in between jobs, the ISO needs to be remounted as the
same time as the virtual fs. Let's manage this case inside the
mount_fs() function.
common: Fixing typo in mount_fs

Prior commit c4cbd801bed2029faaff5cf4b393706a6aa7d3b3, introduced a
badly named variable...
packages: Adding add_epel_repository

In several targets, we need to setup the epel repository to get more
packages for centos or redhat.

Let's make a generic function for that to avoid code duplication.
build: Adding support for RedHatEnterpriseServer

Most of the cases were set for CentOS, let's add RedHatEnterpriseServer
too.
openstack-common: Installing 64bit puppet repo

There is no need to get the 32b while everything is 64.
packages: Say yes to yum update

We shall say yes as per install when performing an update.
openstack-common: Fixing epel repository call

I was using the chroot directory instead of the DIST name... the EPEL
repo wasn't setup at all.
packages: Adding add_satellite_repository()

When SATELLITE_USERNAME and SATELLITE_PASSWORD variables are set, when
running a Redhat OS, the Redhat Network Satellite is configured to get
updates and additional packages.

i.e : puppet package requires rubygems which is only available on the
optional repository.

This patch configure the RHN regarding the user & password given.

Note it requires the "System Group Administrators and Satellite
Administrators" to give the proper rights to SATELLITE_USERNAME.
base.install: Moving rebuild_db

Since we do package installation in add_satellite_repository, we need to
rebuild the db first to avoid mismatching version between host & chroot.
packages: Fixing get_openstack_mirror()

I did a typo when commiting yesterday night. This is a deb type, so we
shall mention it.
init: specify we do IPv4 for now

This to ensure an interface with IPv6 address will be seen as
configured.
init: indent