copr-builders: slightly shorter ssh ControlPath

roles/copr/backend/templates/ssh_config.j2

@@ -6,7 +6,10 @@ Host *
    ServerAliveCountMax 5
    ConnectTimeout 60
 {% if devel %}
-   ControlPath=~/.ssh/.ssh_socket_%h_%p_%r
+   # Be careful with patterns so the socket filename is not too long:
+   # unix_listener: path "/var/lib/resallocserver/.ssh/.ssh_socket_vmhost-x86-copr04.rdu-cc.fedoraproject.org_22_copr.8bslqLJka7WO6iIQ" too long for Unix domain socket: Connection reset by peer
+   # See: https://stackoverflow.com/questions/34829600/why-is-the-maximal-path-length-allowed-for-unix-sockets-on-linux-108
+   ControlPath=~/.ssh/skt_%h_%p_%r
    ControlMaster=auto
    ControlPersist=60
 {% endif %}