maxPrice for InstanceGroup is ignored with LaunchTemplates enabled in aws (spot quote)

[matzegebbe]

1. What kops version are you running? The command kops version, will display
this information.

Version 1.19.0-alpha.3 (git-9cb6797f6781bfa0e40758e84d26bf947824e281)

2. What Kubernetes version are you running? kubectl version will print the
version if a cluster is running or provide the Kubernetes version specified as
a kops flag.

Client Version: version.Info{Major:"1", Minor:"19", GitVersion:"v1.19.0", GitCommit:"e19964183377d0ec2052d1f1fa930c4d7575bd50", GitTreeState:"clean", BuildDate:"2020-08-26T14:30:33Z", GoVersion:"go1.15", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"19", GitVersion:"v1.19.0", GitCommit:"e19964183377d0ec2052d1f1fa930c4d7575bd50", GitTreeState:"clean", BuildDate:"2020-08-26T14:23:04Z", GoVersion:"go1.15", Compiler:"gc", Platform:"linux/amd64"}

3. What cloud provider are you using?
aws
4. What commands did you run? What is the simplest way to reproduce this issue?
Create an instance group with maxPrice set (spot quote)

5. What happened after the commands executed?
maxPrice was ignored and non-spot (on-demand) instances were created
when running kops update cluster, this is show even after running with --yes

  LaunchTemplate/nodes-a.test.dce-t1.xxx.net
  	SpotPrice           	  -> 0.15

  LaunchTemplate/nodes-b.test.dce-t1.xxx.net
  	SpotPrice           	  -> 0.11

6. What did you expect to happen?
see spot requests in aws console / having spot instances instead of on-demand

9. Anything else do we need to know?
using
export KOPS_FEATURE_FLAGS=-EnableLaunchTemplates
fixes the issue.
Since 1.19. LaunchTemplates are used instead of LaunchConfigurations by default