roles/apache: Set ServerName in default SSL vhost

The `ServerName` directive needs to be set inside the default SSL vhost,
as this property does not get inherited from the global configuration,
and it is needs to be set in order for SNI to work correctly.

roles/apache/templates/ssl.conf.j2

@@ -58,7 +58,11 @@ SSLCryptoDevice builtin
 
 # General setup for the virtual host, inherited from global configuration
 #DocumentRoot "/var/www/html"
+{% if apache_server_name is defined %}
+ServerName {{ apache_server_name }}
+{% else %}
 #ServerName www.example.com:443
+{% endif %}
 
 Include conf.d/ssl.include