Ensure all cgroup partitions have a suffix of ".partition"

Ensure all cgroup partitions have a suffix of ".partition"

If the partition named passed in the XML does not already have
a suffix, ensure it gets a '.partition' added to each component.
The exceptions are /machine, /user and /system which do not need
to have a suffix, since they are fixed partitions at the top
level.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>