refactor: use domains' setname as --cert-name option

Certbot has the ability to name a certificate with the --cert-name option.

This allows us for instance to refers to this same setname to other
configuration and then further automate virtualhost creation in nginx or apache.

BREAKING CHANGE: Since this domains' setname was not used, the path was named
after the first domain in the domains set. In order to keep using this workflow,
you need to rename the setname with the first domain in the list like the
following:
```
letsencrypt:
  domains:
    foo.example.com:
      - foo.example.com
```

letsencrypt/domains.sls

@@ -41,8 +41,8 @@
 # represent SubjectAlternativeNames
 create-initial-cert-{{ setname }}-{{ domainlist | join('+') }}:
   cmd.run:
-    - unless: {{ check_cert_cmd }} {{ domainlist[0] }}
-    - name: {{ create_cert_cmd }} certonly --quiet -d {{ domainlist|join(' -d ') }} --non-interactive
+    - unless: {{ check_cert_cmd }} {{ setname }}
+    - name: {{ create_cert_cmd }} certonly --quiet --cert-name {{ setname }} -d {{ domainlist|join(' -d ') }} --non-interactive
       {% if not letsencrypt.use_package %}
     - cwd: {{ letsencrypt.cli_install_dir }}
       {% endif %}
@@ -70,14 +70,14 @@ letsencrypt-crontab-{{ setname }}-{{ domainlist[0] }}:
       - file: {{ renew_cert_cmd }}
       {% endif %}
 
-create-fullchain-privkey-pem-for-{{ domainlist[0] }}:
+create-fullchain-privkey-pem-for-{{ setname }}:
   cmd.run:
     - name: |
-        cat {{ letsencrypt.config_dir.path }}/live/{{ domainlist[0] }}/fullchain.pem \
-            {{ letsencrypt.config_dir.path }}/live/{{ domainlist[0] }}/privkey.pem \
-            > {{ letsencrypt.config_dir.path }}/live/{{ domainlist[0] }}/fullchain-privkey.pem && \
-        chmod 600 {{ letsencrypt.config_dir.path }}/live/{{ domainlist[0] }}/fullchain-privkey.pem
-    - creates: {{ letsencrypt.config_dir.path }}/live/{{ domainlist[0] }}/fullchain-privkey.pem
+        cat {{ letsencrypt.config_dir.path }}/live/{{ setname }}/fullchain.pem \
+            {{ letsencrypt.config_dir.path }}/live/{{ setname }}/privkey.pem \
+            > {{ letsencrypt.config_dir.path }}/live/{{ setname }}/fullchain-privkey.pem && \
+        chmod 600 {{ letsencrypt.config_dir.path }}/live/{{ setname }}/fullchain-privkey.pem
+    - creates: {{ letsencrypt.config_dir.path }}/live/{{ setname }}/fullchain-privkey.pem
     - require:
       - cmd: create-initial-cert-{{ setname }}-{{ domainlist | join('+') }}