Set IdP name on the wayf__idp row

This display name is assumed to be set on the idp row when sending the
request access mail message. Not having it set here will result in the
mail message not being sent.

See point 3 of: https://www.pivotaltracker.com/story/show/180935719

theme/base/templates/modules/Authentication/View/Proxy/Partials/WAYF/idp/idp.html.twig

@@ -13,6 +13,7 @@
     {% if idp['isDefaultIdp'] %}id="defaultIdp"{% endif %}
     tabindex="0"
     data-entityid="{{ idp['entityId'] }}"
+    data-title="{{ idp['displayTitle'] }}"
 >
     <div class="idp__logo">
         {% if idp.logo is not null %}