[DE91]: install_chef_server.sh is not idempotent

[galstrom21]

For some background see: rcbops/opencenter#483

1. install chef server (this works)
2. re-run install chef-server adventure against the same box (this will fail and rollback the original installation)

opencenter-agent/blob/sprint/opencenteragent/plugins/lib/bash/chef/install-chef-server.sh