Bug 14812: Display the help in the correct language

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>
(cherry picked from commit a4ee9151c195a89fe70de792a36f327baa6939f2)
Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>