Multiple participants and 'Pay Later' - and the Contribution record updating process is broken.

Tests with multiple participants and 'Pay Later' - and the Contribution record updating process is broken. The code is now modifying the amount of the Pending pay later contribution record linked to the primary participant to JUST cover his event fee - which is wrong behavior.

To recreate:

• Register for 2 people for sample event 1 (Fall Fundraiser) and w/ Pay Later checked. First fee = Individual (50) and 2nd participant fee = Couple ($100)
• You'll have a pending contribution record for $150
• Edit the primary participant and set Participant status = Registered and Contribution status = Completed
• We wind up with a completed $50 contribution RATHER THAN the expected $150 contribution.