Make `etcd_bin_prefix` configurable

🗣️ Foreword

Thank for taking the time to fill this feature request fully. Without it we may not be able to , and the issue may be closed without resolution.

🙍 Problem Statement

I would love to be able to configure the folder where the etcd binaries are installed. We want to install two different versions on a single server.

❔ Possible Solution

I can see that the etcd_bin_prefix is currently hard coded:

etcd/resources/etcd_installation_binary.rb

Lines 66 to 68 in 9b26b2c

    
           def etcd_bin_prefix 
        
             '/usr/bin' 
        
           end

We would like to make it a property, just like the version for instance.

This prefix should also be configurabe in etcd_service_manager_systemd.

If this is something interesting for you, we developed a PR (Scalingo#1) which can be backported here.

⤴️ Describe alternatives you've considered

We considered using etcd_installation_docker (rather than etcd_installation_binary currently) but it would be a lot of work. Moreover it seems impossible to change the mounted volumes but we need it to mount the TLS files inside the etcd container.

➕ Additional context

n/a