common: Get rid of umounted /dev/ /proc

When entering the cleanup, we have to disable the "-e" option unless any
command that fails in the cleanup() will not be executed...

As the clean-mountpoints is part of cleanup, this is mandatory to insure
that /dev/ & /proc are properly umounted.
base.install: Adding init_redhat_chroot()

This function is made to manage everything about creating an initial
chroot for every kind of redhat & derivatives.

This include creating the rpm deb, initial pkg install, adding gpg keys
and cleaning rpm db if version mismatch between host & chroot.
common: Let's umount dirs by considering longest path first

When umounting, it's faster to umount the longest path first like
/dev/pts before /dev.
common: Adding missing awk

Was missing from my last commit.
packages: ignore yum check-update returned code

“yum check-update” execution code is not really useful, we ignore it for
the moment.

Retcode:
 - 0: success
 - 100: success with update packages to install
 - 0: RHN communication failure ( https://access.redhat.com/site/solutions/72573 )
base: do not reinstall hpacucli on CentOS 2

rpm will returns a failure if we try to reinstall a rpm.
openstack: add an empty “exclude” file