[terraform] Default value for hana_cluster_fencing_mechanism in different cloud providers

[mpagot]

AWS --> native

qe-sap-deployment/terraform/aws/variables.tf

Line 300 in 9b338bc

default = "native"

AZURE --> sbd

qe-sap-deployment/terraform/azure/variables.tf

Line 412 in 9b338bc

default = "sbd"

GCP --> native https://github.com/SUSE/qe-sap-deployment/blob/main/terraform/gcp/variables.tf#L345

[mpagot]

It is not about what is working or what is expected to be supported, it is just about the proposed default value in the variables.tf
default is not always the same and I feel, from user point of view, maybe it could be better to use same default.