Address incomplete chain error

Fix Apache's configuration for version 2.4.8 and above.  See
https://community.letsencrypt.org/t/untrusted-on-mobile-newbe/7903

roles/common/templates/etc_apache2_conf-available_ssl.conf.j2

 SSLStaplingReturnResponderErrors off
 
 SSLCertificateKeyFile	/etc/letsencrypt/live/{{ domain }}/privkey.pem
-SSLCertificateFile	/etc/letsencrypt/live/{{ domain }}/cert.pem
+SSLCertificateFile	/etc/letsencrypt/live/{{ domain }}/fullchain.pem
 SSLCertificateChainFile	/etc/letsencrypt/live/{{ domain }}/chain.pem
 
 SSLCipherSuite ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-DSS-AES128-GCM-SHA256:kEDH+AESGCM:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA:ECDHE-ECDSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-DSS-AES128-SHA256:DHE-RSA-AES256-SHA256:DHE-DSS-AES256-SHA:DHE-RSA-AES256-SHA:!aNULL:!eNULL:!EXPORT:!DES:!RC4:!3DES:!MD5:!PSK