nova-multi-controller nodes cannot be ceph-store/swift-storage too

There's a conflict in how additional disks are used between all those
roles.

https://bugzilla.novell.com/show_bug.cgi?id=774317
(cherry picked from commit 44324173a14a7922a9f34499556ea3300e7be567)

Signed-off-by: Ralf Haferkamp <rhafer@suse.de>
Use third validation step for proposals

We don't want destructive validation.
(cherry picked from commit c784c164161afc0c3ff2f61d09ebc0e9bb7334e8)

Signed-off-by: Ralf Haferkamp <rhafer@suse.de>
Raise one exception with all errors for the validation

It's better to display all errors at once.
(cherry picked from commit baec2492a7346d8865866c895f4c0d463441dcdf)

Signed-off-by: Ralf Haferkamp <rhafer@suse.de>
only restart libvirtd if needed (bnc#776938)
(cherry picked from commit bd6ad49f3ce8716eac39ae7b6ec78d534e9c03a5)

Signed-off-by: Ralf Haferkamp <rhafer@suse.de>