Move Policy Storage to RWO

Move Policy Storage to RWO

Today when deploying Policy with OOM, the PersistentVolumeClaim needs the
"ReadWriteMany" (or "RWX") capability.

According to Kubernetes Documentation (https://kubernetes.io/docs/concepts/storage/persistent-volumes/#access-modes),
ReadWriteMany stands for "the volume can be mounted as read-write by many nodes".

That means that a particular PVC needs to be read and written from many pods.
That also means that your code takes that into account and do the work to avoid
write at the same place at the same time.

An issue on RWX mode is that most "official" storage driver from Kubernetes doesn't
support it (13 over the 19 drivers doesn't support it, espacially OpenStack, Amazon
and Google storage classes).

Policy PVC for Nexus and Policy PVC for mariadb are  used only for one POD.
Thus we don't need RWX.

Change-Id: Idf8a6ba8ef14ce7ca397438c2200c11517d0458e
Issue-ID: POLICY-2019
Signed-off-by: Sylvain Desbureaux <sylvain.desbureaux@orange.com>