Remove duplicate when statement in Let's Encrypt task

While adding the Let's Encrypt offline testing block in 1746afcc we
accidentially duplicated a the 'when' statement. Ansible only looks at
the last when statement for a given block meaning the earlier one has no
use. This commit merges both lines in one.

roles/common/tasks/letsencrypt.yml

   shell: cat /etc/letsencrypt/live/{{ domain }}/cert.pem
     /etc/letsencrypt/live/{{ domain }}/chain.pem >
     /etc/letsencrypt/live/{{ domain }}/fullchain.pem
-  when: private_key.changed or certificate.changed or ca_certificate.changed
-  when: ansible_ssh_user == "vagrant"
+  when: (private_key.changed or certificate.changed or ca_certificate.changed) and ansible_ssh_user == "vagrant"
 
 - name: Set permissions on combined SSL public cert
   file: name=/etc/letsencrypt/live/{{ domain }}/fullchain.pem mode=0644