connection: simplify reply cleanups

connection: simplify reply cleanups

There is no reason why we cannot destroy replies while holding a
connection lock. If the reply points to the connection whose lock we hold,
we also have another ref on that connection due to our context. If the
lock points to another connection, we can simply unref it at any time.

Note that we never cause disconnects on the connection. We only unref it!
The object destruction is a simple memory cleanup. Nothing fancy is done
there, and no inter-object refs can exist anymore (otherwise, it would not
get freed). Therefore, fix all our callers to free replies directly,
instead of releasing the locks first.

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>