Merge pull request #86 from bottlerocket-os/bugbash-readme

Updated Readme.md to mention minimum Bottlerocket version requirement

Author: srgothi92

README.md

@@ -61,6 +61,10 @@ A container instance may be skipped for update when:
   If draining has not completed by the end of the period, the updater will restore the instance and move to the next one.
   The time it takes for a task to be stopped is related to the `stopTimeout` task definition parameter and to any associated resources like load balancers.
   If your tasks are taking too long to drain, you can ensure that your task responds to `SIGTERM`, shorten the `stopTimeout`, or shorten the load balancer's health check and deregistration delay settings.
+* _Bottlerocket version is too old._
+  The Bottlerocket ECS Updater uses newer [`apiclient update` commands](https://github.com/bottlerocket-os/bottlerocket#update-api) that were added in version [1.0.5](https://github.com/bottlerocket-os/bottlerocket/blob/develop/CHANGELOG.md#v105-2021-01-15).
+  The SSM commands will fail if your Bottlerocket OS version is less than 1.0.5.
+  Instances running Bottlerocket versions less than 1.0.5 need to be manually updated.
 
 ### Why do new container instances launch with older Bottlerocket versions?