chg: dev: Use a suitable response in tcp_connected() when initiating a read

When 'ISC_R_TIMEDOUT' is received in 'tcp_recv()', it times out the
oldest response in the active responses queue, and only after that it
checks whether other active responses have also timed out. So when
setting a timeout value for a read operation after a successful
connection, it makes sense to take the timeout value from the oldest
response in the active queue too, because, theoretically, the responses
can have different timeout values, e.g. when the TCP dispatch is shared.
Currently 'resp' is always NULL. Previously when connect and read timeouts
were not separated in dispatch this affected only logging, but now since
we are setting a new timeout after a successful connection, we need to
choose a suitable response from the active queue.

Merge branch 'aram/dispatch-tcp_connected-fix' into 'main'

See merge request isc-projects/bind9!9927