try to disable ipv6 default route configuration in servers when re6st is used.

/reviewed-on !62

/reviewed-on nexedi/slapos.package!68

I lost the old key so I regenerated a new one... (this time I'll keep a backup...)

/reviewed-on nexedi/slapos.package!67

Some servers failed to run upgrader because slapos.libnetworkcache was old and not compatible anymore. So playbook couldn't be downloaded.
We check if slapos.libnetworkcache and slapcache need to be upgraded before run upgrader role.

/reviewed-on nexedi/slapos.package!65

  On the KVM, we can be slowdown on a single process, however we can reach the maximum io speed
  if we have a good configuration.

/reviewed-on nexedi/slapos.package!64

This reverts commit 15b2692c.
This change was committed directly on slapos.git: nexedi/slapos@1f46a963

/reviewed-on nexedi/slapos.package!61

/reviewed-on nexedi/slapos.package!60

  Remember that this workarround must be removed once the implementation changes to use caucase. 

Signing key has been recreated and repository/projects updated with the new key, everything should be fine now so we can remove workarounds in playbooks (insecure repository updating)

/reviewed-on nexedi/slapos.package!59

There's no `find` module on Ansible 1.7 so we need to use the `find` command directly instead.

/reviewed-on nexedi/slapos.package!57

fd46::/64 is a randomly chosen value within fc00::/16

/reviewed-on nexedi/slapos.package!54

All network access shall be protected if Ansible is run in offline mode.

/reviewed-on nexedi/slapos.package!53

This reverts commit 5fe5177f

For now the mitogen don't work on 2.5 which is the version installed by more recent centos.

/reviewed-on nexedi/slapos.package!52

It is important to have them in case of problem analysis.

The most important thing is that Certificate has to match the Key.

The CA certificate is fully optional, so make it seen as this, and also
explain what is its purpose.