Remove invalid pledge payment statuses from Contribution form when recording a pledge payment

Currently we allow users to set "invalid" statuses from the "Record Pledge Payment" form (edit contribution w/ ppid parameter). See this forum post for results:

http://forum.civicrm.org/index.php/topic,10158.0.html

This results in an uneditable pledge payment record.

We should supress invalid statuses - In Progress, Failed (and possibly Cancelled).