Front end membership purchase ignores payment processor status id if the membership is recurring

Some payment processors (IATS, also possibly eWay?) return a contribution status id. This is ignored when purchasing a membership via credit card if the membership is recurring. Therefore the initial payment gets created as pending even if it was successful and the membership is also pending.

To reproduce:

• Setup the IATS processor with the test credentials.
• See https://github.com/iATSPayments/com.iatspayments.civicrm/blob/master/README.md for those
• Create a membership type with fees that will validate with the test processor
  EG. $3.00/mth and with the auto-recur option.
• Create a membership page for this membership type using quick config
• Use this page to purchase a recurring membership via credit card (IATS) and choose to have it automatically recur. (Use the test visa 4222222222222220 etc.)
• Even though the first payment goes through in the payment processor the payment is recorded as pending and so is the membership
• IPN is not used for IATS so the membership will never move out of pending
  See also CRM-16044 for the backend case - now fixed!