t/loc_tools: Don't return duplicates

Make sure the return of find_locales() (and hence any internal subs
that call it) has no repeated locale names.

t/loc_tools.pl

@@ -679,7 +679,9 @@ ($;$)
         }
     }
 
-    @Locale = sort @Locale;
+    my %Locale;
+    $Locale{$_} = 1 for @Locale;
+    @Locale = sort keys %Locale;
 
     return @Locale;
 }