Return 200 for incomplete reimbursement errors

These do not need any further processing by wombat.  They need to be
picked up by customer service and processed manually. Thus, there's
not much point to marking them as failed in Wombat.

It makes me a little nervous to return a 200 OK in a situation like
this but from wombat's perspective there isn't anything further to
do and the alternative of spamming wombat with extraneous failures
seems worse.