Bug 8952: (follow-up) using_https does not deal with Plack

Bug 8952: (follow-up) using_https does not deal with Plack

When using Plack, the https method returns 'OFF'.
We have to test this value before sending the value to templates.

Test plan:
1/ Fill your OPACBaseUrl

2/ Configure apache for using http
3/ Check the social networks links (should be http://OPACBaseUrl)

4/ Launch Plack
5/ Check the social networks link (should be http://OPACBaseUrl)
6/ Stop Plack

7/ Configure apache for using https
  sudo openssl req -x509 -nodes -days 365 -newkey rsa:1024 -out
/etc/apache2/server.crt -keyout /etc/apache2/server.key
and add in you virtualhost (with :443)
    SSLEngine on
    SSLCertificateFile /etc/apache2/server.crt
    SSLCertificateKeyFile /etc/apache2/server.key
  a2enmod ssl
  service apache2 restart
8/ Check the social networks links (should be https://OPACBaseUrl)

FIXME: Under Plack, with ssl actived, the CGI->https() method always
returns 'OFF'.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>