Added handler for ASG MixedInstancesPolicy

* Enables the ASG instance type to be determined from the LaunchTemplate
default
* This makes it possible to have a mixed instance ASG, relying on AWS'
native logic for things like on-demand launch priority and spot
instances etc

cluster-autoscaler/cloudprovider/aws/auto_scaling_groups.go

@@ -388,6 +388,9 @@ func (m *asgCache) buildAsgFromAWS(g *autoscaling.Group) (*asg, error) {
 func (m *asgCache) buildLaunchTemplateParams(g *autoscaling.Group) (string, string) {
 	if g.LaunchTemplate != nil {
 		return aws.StringValue(g.LaunchTemplate.LaunchTemplateName), aws.StringValue(g.LaunchTemplate.Version)
+	} else if g.MixedInstancesPolicy != nil && g.MixedInstancesPolicy.LaunchTemplate != nil {
+		return aws.StringValue(g.MixedInstancesPolicy.LaunchTemplate.LaunchTemplateSpecification.LaunchTemplateName),
+			aws.StringValue(g.MixedInstancesPolicy.LaunchTemplate.LaunchTemplateSpecification.Version)
 	}
 
 	return "", ""