Set default locale for the intl extension upon locale detection

refs #6778

library/Icinga/Util/Translator.php

@@ -3,6 +3,7 @@
 
 namespace Icinga\Util;
 
+use Locale;
 use Icinga\Exception\IcingaException;
 
 /**
@@ -173,7 +174,9 @@ class Translator
                     $localeName
                 );
             }
+            Locale::setDefault(static::DEFAULT_LOCALE);
         } else {
+            Locale::setDefault($localeName);
             $locale = setlocale(LC_ALL, 0);
             putenv('LC_ALL=' . $locale); // Failsafe, Win and Unix
             putenv('LANG=' . $locale); // Windows fix, untested