BUG-8372: improve forward/replay naming

There is a bit of confusion between 'replay' and 'forward' methods.
They serve two distinct purposes:
- 'replay' happens during reconnect, i.e. for requests that have
           already entered the connection queue and have paid
           the delay cost, so they should not pay it again.
- 'forward' happens after reconnect for requests that have raced
            with the reconnect process, i.e. they need to hop from
            the old connection to the new one. These need to enter
            the queue and pay the delay cost.

This patch cleans the codepaths up to use consistent naming, making
it clearer that the problem we are seeing is in the 'replay' path.

Change-Id: Id854e09a0308f8d0a9144d59f41e31950cd58665
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>
(cherry picked from commit cc21df8ade11f41843dc558e8fc93d5be92ed151)