When a request comes back from the waiting list, it is accounted for in
the client_req counter, despite not being a new request. To avoid the
spurious increments, a request is counted only after leaving the state
machine for good. This has no effect on when the client_req increment
becomes visible since it is part of the "wrk" group in the first place.

In 2e66e0b9 the client_req increment was
moved from the request state machine (R_STP_TRANSPORT) to individual
transport. This patch can't be reverted because shortly aftwerwards the
ESI transport changed in 2c59afe2 and
now runs the R_STP_TRANSPORT step and the client_req counter does not
count sub-requests.

Refs 2e66e0b9
Refs 2c59afe2