Interop scenario doc - scenario 5.1

[Doug Davis <dug@us.ibm.com>]

For scenario 5.1 ReplayCommit it current
shows this flow:

Initialization

IA sends an application message tns:ReplayCommit request to PA containing CoordinationContext.
PA registers PS1 and PS2 with CS for a Durable2PC protocol.
PA responds with an application reply tns:Response.

Message Exchange

        (IA initiates Commit)

1. CS sends Durable2PC::Prepare to PS1
2. PS1 sends Durable2PC::Prepared to CS
3. CS sends Durable2PC::Prepare to PS2
4. PS2 sends Durable2PC::Prepared to CS
5. CS sends Durable2PC:Commit to PS1
6. PS1 sends Durable2PC::Committed to CS
7. CS sends Durable2PC::Commit to PS2
   (CS commits the transaction. PS2 suffers from internal failure)
8. Upon recovery, PS2 sends 2PC::Prepared to CS
9. CS re-sends Durable2PC::Commit to PS2
10. PS2 sends Durable2PC::Committed to CS

I believe this is wrong.
1 - The "(CS commits the transaction)"
should come after step 10 - meaning the Coordinator should not exit the
"Committing" stage until it receives Committed from all of the
participants
2 - Something should block resent "Commit"
messages from the Coordinator (if any) until PS2 has a chance to resend
its "Prepared" message - since the point of the test is how the
Coordinator deals with extra Prepared messages while in the Committing
stage.

Not sure who has the pen but i think
we should update the doc to correct this - something like:

1. CS sends Durable2PC::Prepare to PS1
2. PS1 sends Durable2PC::Prepared to CS
3. CS sends Durable2PC::Prepare to PS2
4. PS2 sends Durable2PC::Prepared to CS
5. CS sends Durable2PC:Commit to PS1
6. PS1 sends Durable2PC::Committed to CS
7. CS sends Durable2PC::Commit to PS2
   (PS2 suffers from internal failure)
   (PA prevents any resent Commit from reaching PS2 - simulating failure)
8. Upon recovery, PS2 sends 2PC::Prepared to CS
9. CS re-sends Durable2PC::Commit to PS2
10. PS2 sends Durable2PC::Committed to CS
    (CS commits the transaction)

Not sure what the purpose of PS1 is
(and would prefer to remove it) but oh well  :-)

thanks
-Doug