The _MAX_RESERVED_SOCKETS cap applied to pinned CIMD sockets too, so under
heavy concurrency an ephemeral-reservation churn could close a parked pinned
socket before _wait_for_callback adopted it, silently reopening the
port-stealing window the pin exists to prevent (#22161). Eviction now skips
the pinned range; it is already bounded by _CIMD_PORTS.
Follow-up to the #84050 salvage.
Teknium