Create templates for global storage use

Two helper functions are defined:

- common.storageClass: will print the right storage class according to
  properties set or not:
  * if no storage class set --> use previous behavior (storage class
    named `common.fullname-data`.
  * if a "persistence.storageClassOverride" is set for this specific chart,
    we use it (if it's "-", we set to default one)
  * if a "global.persistence.storageClass" has been set (and no
    storageClassOverride for this chart), we use it (same specificity than
    storageClassOverride)
  * if a "persistence.storageClass) has been set (and no
    storageClassOverride nor global one), we use it (same specificity
    than storageClassOverride)

- common.needPV: will print "True" if we need a PV (no storageClass and
  storageClassOverride being set).

an implementation example with mariadb-galera is provided.

Issue-ID: OOM-1500
Change-Id: I20a667e17b00c255c4b828e3c66f9c0df7c8755c
Signed-off-by: Sylvain Desbureaux <sylvain.desbureaux@orange.com>
diff --git a/kubernetes/common/mariadb-galera/values.yaml b/kubernetes/common/mariadb-galera/values.yaml
index a662b1e..14215e4 100644
--- a/kubernetes/common/mariadb-galera/values.yaml
+++ b/kubernetes/common/mariadb-galera/values.yaml
@@ -35,7 +35,7 @@
 #repository: mysql
 repository: nexus3.onap.org:10001
 image: adfinissygroup/k8s-mariadb-galera-centos:v002
-backupImage: library/mariadb:10.1.38 
+backupImage: library/mariadb:10.1.38
 imageInit: busybox
 pullPolicy: IfNotPresent
 
@@ -91,7 +91,7 @@
   mountSubPath: "mariadb-galera/data"
   mysqlPath: /var/lib/mysql
   backup:
-    mountPath: /dockerdata-nfs/backup
+    mountPath: /dockerdata-nfs/backup{{- if or (or .Values.storageClassOverride .Values.persistence.storageClass) .Values.global.persistence.storageClass -}}
 
 service:
   internalPort: 3306