sap_ha_pacemaker_cluster: Enhance corosync totem handling

[marcelmamula]

Changes:

• Add __sap_ha_pacemaker_cluster_corosync_totem_default in OS variable files with baseline corosync totem settings
• Add __sap_ha_pacemaker_cluster_corosync_totem_platform in Platform variable files with recommended corosync totem settings
• Rework logic inside of construct_vars_common.yml to become dynamic - Platform totem is combined with OS totem, where Platform can overwrite OS values as required.

# Prepare corosync totem variable with either:
# - User provided sap_ha_pacemaker_cluster_corosync_totem if present
# - Combine corosync totem from OS variables and Platform variables if present
# - Use default corosync totem from OS variables if Platform variable is not present

Tested on:

• SLES15 SP5 - SAP ASCS/ERS and HANA clusters

Note 1:
This change is now applicable to SUSE after changes in ha_cluster linux-system-roles/ha_cluster#212

Note 2:
Platform specific totem values are taken from comprehensive configuration in crmsh https://github.com/ClusterLabs/crmsh/blob/master/etc/profiles.yml

[ja9fuchs]

lgtm

[sean-freeman]

Very sensible/logical approach, lgtm 👍