crowbar_join.suse: Always install chef handlers

Install chef reboot handlers also if /etc/chef/client.rb is
already available.
> Thinking more about this: do you think there's a chance that this handler is called with a very small uptime, then breaking the uptime detection in crowbar? Maybe it'd be better to save the time instead, and then compare that with the "now - uptime" in crowbar?

Theoretically that's possible. But `:wait_for_reboot_uptime` is written *after* the chef-client run. And the chef-client run needs some time. After the reboot the uptime is collected *before* the chef-client run (in fact when sshd is ready which is started before crowbar_join).  So I would say that's not a problem.