test(e2e): start a mock uploader once the client has registered it

The mock peers signalled ready as soon as their PeerInit was written,
and the tests slept 1.5 s before downloading so the client could
register the connection. A download that got in first dialled a peer
the server has never heard of, and since CantConnectToPeer fails queued
downloads it failed at once instead of waiting for the connection.

A mock now asks for the client's user info before signalling ready. The
client answers through the peer it registered for that connection, so
the answer means the download will queue on it. The six sleeps go.

soulseek-rs-lib/tests/e2e.rs

@@ -533,7 +533,14 @@ fn open_control_and_await_queue(
     let mut p = connect_retry(&cfg.listen_addr, Duration::from_secs(5))?;
     p.set_read_timeout(Some(Duration::from_secs(10)))?;
     p.write_all(&peer_init_bytes(&cfg.peer_username, "P", 0))?;
+    // The client answers a user-info request through the peer it registered
+    // for this connection, so the answer means a download queues on it
+    // rather than dialling a peer the server has never heard of.
+    p.write_all(
+        &soulseek_rs::message::peer::build_user_info_request().get_buffer(),
+    )?;
     p.flush()?;
+    expect_code(&mut p, 16, Duration::from_secs(10))?;
     let _ = cfg.ready.send(());
 
     loop {
@@ -867,10 +874,6 @@ fn file_downloads_over_p_and_f(
         .recv_timeout(Duration::from_secs(5))
         .expect("mock uploader P connection");
 
-    // The listener registers an incoming peer under its plain username; give
-    // that registration a moment to complete before queuing the download.
-    std::thread::sleep(Duration::from_millis(1500));
-
     let (_download, status_rx) = client
         .download(
             filename.to_string(),
@@ -950,7 +953,6 @@ fn cancel_mid_transfer(peer_username: &str, stall_after: Option<usize>) {
     ready_rx
         .recv_timeout(Duration::from_secs(5))
         .expect("mock uploader P connection");
-    std::thread::sleep(Duration::from_millis(1500));
 
     let (_download, status_rx) = client
         .download(
@@ -1050,7 +1052,6 @@ fn a_cancelled_queued_download_declines_the_peers_offer() {
     ready_rx
         .recv_timeout(Duration::from_secs(5))
         .expect("mock uploader P connection");
-    std::thread::sleep(Duration::from_millis(1500));
 
     let download_dir = unique_download_dir();
     let (_download, status_rx) = client
@@ -1124,7 +1125,6 @@ fn refusal_fails_the_download_quickly(
     ready_rx
         .recv_timeout(Duration::from_secs(5))
         .expect("mock uploader P connection");
-    std::thread::sleep(Duration::from_millis(1500));
 
     let download_dir = unique_download_dir();
     let (_download, status_rx) = client
@@ -1224,7 +1224,6 @@ fn an_interrupted_download_resumes_from_its_partial_file() {
     ready_rx
         .recv_timeout(Duration::from_secs(5))
         .expect("mock uploader P connection");
-    std::thread::sleep(Duration::from_millis(1500));
 
     let (_download, status_rx) = client
         .download(
@@ -3359,7 +3358,6 @@ fn download_progress_reports_the_rate_actually_received() {
     ready_rx
         .recv_timeout(Duration::from_secs(5))
         .expect("mock uploader P connection");
-    std::thread::sleep(Duration::from_millis(1500));
 
     let (_download, status_rx) = client
         .download(