Bug 14812: Display the help in the correct language

If opaclanguages != language, the language of the help page is the
default one (en).

Test plan:
1/ Set language to en, fr-FR, ar-Arab and opaclanguages to en, fr-FR
2/ Translate the fr-FR and ar-Arab templates.
3/ Go on the mainpage, switch to ar-Arab, go to the help page.
The help page content should be in Arabian, not English.

Signed-off-by: Magnus Enger <magnus@libriotech.no>
Set language = en, sv-SE, nb-NO. opaclanguage = en, nb-NO
Went to the intranet main page, selected Swedish and clicked on help
Without the patch, help was displayed in English
With the patch, help was displayed in Swedish. Yay!

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>

help.pl

@@ -39,6 +39,10 @@ sub _help_template_file_of_url {
 
 my $query = new CGI;
 
+# Init the interface to get the correct language.
+# This is usually set by get_template_and_user
+C4::Context->interface('intranet');
+
 # find the script that called the online help using the CGI referer()
 our $refer = $query->param('url');
 $refer = $query->referer()  if !$refer || $refer eq 'undefined';