Nova can fill up the partition that /var/lib/libvirt/qemu/save is on
when nova calls `image-create` on an instance. This occurs because
nova calls libvirt with managedsave which creates a temporary file in
the /var/lib/libvirt/qemu/save location. Libvirt does not allow the
location of /var/lib/libvirt/qemu/save to be configurable so we have
to manage it ourselves via bindmounts or symlinks.
In this commit we remove the /var/lib/libvirt/qemu/save directory and
create a symlink in it's place, pointing to
`{{ nova_system_home_folder }}/save` instead (which we also create).
This location was chosen as deployers often have more space here for
nova instances.
Change-Id: I5c96f70aa355cc02379fe7e0681416eca53447eb
Partial-Bug: #1585325
(cherry picked from commit 2599006a81)
066012914e