MDL-43131 qbank: Fix show question text when first viewing.

When you followed the link to the question bank, the checkbox for the
"Show question text in the question list" option correctly reflected the
user's preference, but what was actually shown in the question bank did
not.

question/editlib.php

@@ -932,7 +932,7 @@ class question_bank_view {
         $columns = array('checkbox', 'qtype', 'questionname', 'editaction',
                 'previewaction', 'moveaction', 'deleteaction', 'creatorname',
                 'modifiername');
-        if (optional_param('qbshowtext', false, PARAM_BOOL)) {
+        if (question_get_display_preference('qbshowtext', 0, PARAM_BOOL, new moodle_url(''))) {
             $columns[] = 'questiontext';
         }
         return $columns;