[PORTAL] Use global storage templates for PVC

[PORTAL] Use global storage templates for PVC

OOM has now templates in order to create the needed PVC, using:

* a PV with a specific class when using a common nfs mount path between
nodes (sames as today use) --> is the default behavior today
* or a storage class if we want to use dynamic PV.
  On this case, we use (in order of priority):
  - persistence.storageClassOverride if set on the chart
  - global.persistence.storageClass if set globally
  - persistence.storageClass if set on the chart

Change-Id: I28b4ac5f612de75918973148865cf82f7a7de5e8
Issue-ID: OOM-1227
Signed-off-by: Sylvain Desbureaux <sylvain.desbureaux@orange.com>