[PW-2015]: Fix orders not being created but card getting charged when Persistent Cart and Guest Checkout enabled (#630)

* [PW-2015]: Fix orders not being created but card getting charged when Persistent Cart and Guest Checkout enabled

* [PW-2015]: Removing \Magento\Checkout\Model\Session DI not being used anymore

* Skipping payment validation if no quoteId is present

* Replacing ternary check with if/else for readability