Set translation fallback to False per default

i18n.translate() is used for L10N whereas i18n translations
are done by i18n.tntranslate. Because L10N is site-dependend and not language-dependent, fallback must be False per default.
Otherwise the given results (templates, categories etc.) may be wrong.

Change-Id: Id618817ba7a798733117b202f524ad4695099035
Merge "Set translation fallback to False per default"