library/roles/sshd_config: Use a variable to optionally skip the task.

d4science-ghn-cluster/group_vars/dataminer_garr/dataminer_garr.yml: Do not install sshd_config.

sshd_config/defaults/main.yml

@@ -1,4 +1,5 @@
 ---
+sshd_install_config: True
 sshd_port: 22
 sshd_config_dir: /etc/ssh
 sshd_config_file: sshd_config

sshd_config/tasks/main.yml

@@ -2,4 +2,5 @@
 - name: Install the sshd configuration file
   template: src=sshd_config.j2 dest={{ sshd_config_dir }}/{{ sshd_config_file }} owner=root group=root mode=0644
   notify: Reload the ssh service
+  when: sshd_install_config
   tags: [ 'ssh', 'sshd_config' ]