Revert "Client: eliminate SetExpired(), call Close() directly"

This reverts commit 58d7804d66.  It
caused a use-after-free bug when Client::OnSocketError() was called
due to a failed write, e.g. if the output buffer was full.

src/client/Read.cxx

@@ -69,5 +69,10 @@ Client::OnSocketInput(void *data, size_t length) noexcept
 		return InputResult::CLOSED;
 	}
 
+	if (IsExpired()) {
+		Close();
+		return InputResult::CLOSED;
+	}
+
 	return InputResult::AGAIN;
 }