Support multiple processes in sidekiq:install

[lloydwatkin]

This updates the uploading of systemd service files for multiple process sidekiq workers. It does not break existing codebases by implementing a naming structure like sidekiq@1.service where only a single process is requested.

Connects to #298

[jclusso]

@lloydwatkin what is the purpose of this? This doesn't make sense to me since you don't need multiple systemd files to support multiple processes.

The naming of the service file with an @ on the end is the standard way to specify that it is a multi process service. You can then run commands like systemctl [start|stop|status] sidekiq@1 or even more do stuff to multiple processes at the same time with systemctl [start|stop|status] sidekiq@{1..2}.

[jclusso]

@lloydwatkin I think I understand what the reason for this was but it's not correct. The @ sign in the service file name is a special argument and what comes after it is passed into the service file. Having the naming be the same for a single process and a multi process system does not look possible. It appears we should have both sidekiq.service and sidekiq@.service. You can read more about it here.