Don't use dynamic object properties

[andrewbelcher]

ContactsTabManager::verifyTab uses $block->_contactTabVerified, a dynamically set property on the blocks. This breaks property optimisation (see https://www.drupal.org/node/2531564) and so we shouldn't do it.

It's possible there are other places we've done this...

[andrewbelcher]

This use case would be better solved by a defined property on the tab, something like $verifiedBlocks...