Update RDS Instance Relation For Roles

[mabuaisha]

It seems that cloudify.relationships.aws.rds.instance.connected_to relationship for role need to be updated when associating multiple roles with RDS Instance because the current code right now suppose that iam_role_type_key & iam_role_id_key should not be both exists when having relationship with RDS Instance which is wrong and need to be updated

    - type: cloudify.relationships.aws.rds.instance.connected_to
      target: my_monitoring_iam_role
      source_interfaces:
        cloudify.interfaces.relationship_lifecycle:
          preconfigure:
            inputs:
              iam_role_type_key: MonitoringRoleArn
    - type: cloudify.relationships.aws.rds.instance.connected_to
      target: my_domain_iam_role
      source_interfaces:
        cloudify.interfaces.relationship_lifecycle:
          preconfigure:
            inputs:
              iam_role_type_key: DomainIAMRoleName

The code need to be updated so that we can force both attributes to be passed when attaching roles to RDS Instance

Code need to be updated here https://github.com/cloudify-cosmo/cloudify-aws-plugin/blob/master/cloudify_aws/rds/resources/instance.py#L181

And we need also to update the examples https://github.com/cloudify-cosmo/cloudify-aws-plugin/blob/master/examples/rds-feature-demo/blueprint.yaml#L94

[EarthmanT]

#RD-2909