[bamboo server] environment usage "bamboo_deploy_version_previous"

[Bill Wang]

I used this bamboo environment bamboo_deploy_version_previous in a rollback task.

I have a deploy task called deploy2prod, for example, currently it is release-22

It will rename the old containers to <projectId>-release-21 first, then deploy a new service.  release-21 is the release number of previous deployment.

I added another rollback task after prod release. Will only start it if required.

I still use bamboo_deploy_version_previous as variable to get the name of <projectId>-release-21, but I found this rollback task is failed. It always tries to get the current release number <projectId>-release-22

Seems a bug for me, need confirm with Bamboo develop team.

### Updates

In bamboo logs,  deployment task deploy2prod, bamboo_deploy_version_previous and bamboo_deploy_version are diffrerent: 

amboo_deploy_version_previous=release-21

bamboo_deploy_version=release-22

But in rollback task,  both bamboo_deploy_version_previous and bamboo_deploy_version are same

bamboo_deploy_version_previous=release-22

bamboo_deploy_version=release-22