fix/debugging aid for a type of duplicate payments

fix/debugging aid for a type of duplicate payments

I haven't been able to reproduce this but I've seen logs where a given
transaction id and payment amount was listed more than once for a given
payment request (open-ils.circ.money.payment).  I can imagine this
happening if util.list is lying to us when we call .dump_retrieve_ids
against the bill list.  This changeset catches that, but since it is
more of a workaround than a true fix, we also warn the user and attempt
to gather more information that may help us pin this down.

Signed-off-by: Jason Etheridge <jason@esilibrary.com>