Call _tearDown when logging out.

This is necessary for cleaning up after tests (now that each test has its own
initialized converse).

Should hopefully not cause any issues when logging out during normal use.

src/converse-core.js

@@ -535,12 +535,13 @@
 
         this.logOut = function () {
             converse.disconnection_cause = converse.LOGOUT;
-            converse.chatboxviews.closeAllChatBoxes();
-            converse.clearSession();
             if (typeof converse.connection !== 'undefined') {
                 converse.connection.disconnect();
                 converse.connection.reset();
             }
+            converse.clearSession();
+            converse._tearDown();
+            converse.chatboxviews.closeAllChatBoxes();
             converse.emit('logout');
         };