Fix path for ssh key file

This commit fixes the path to be the proper location instead of a
template param to make things actually work.

Change-Id: I155b3cdaa9ff472653420472fdd01e43613d11f9

templates/germqtt.conf.erb

@@ -4,7 +4,7 @@ pidfile = <%= @pid_file %>
 [gerrit]
 username = <%= @gerrit_username %>
 hostname = <%= @gerrit_hostname %>
-key = <%= @gerrit_key %>
+key = /home/germqtt/.ssh/id_rsa
 
 [mqtt]
 hostname = <%= @mqtt_hostname %>