HOTFIX: No serverside synchronous online check

Found this while updating for branch "force_sync" (https://github.com/learningequality/ka-lite/pull/529)

In fact #178 was not fully fixed--the synchronous check for online status still exists for the easy_admin page--even though it's no longer used.  This causes admins to have to wait while that request times out.

To completely fix that bug, we need to remove this check, and let users proceed to the page directly, where we check this status using AJAX/JsonP.