ssh/test: work around for TestCiphers failures on macOS

TestCiphers is already skipped on macOS when testing data received
from the server, so move the test for sending data after the
receiving one to work around this new integration test failure.

Fixes golang/go#65732

Change-Id: Ie0c614c5373735ae8aefdd7ded643579b130f4b3
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/564457
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Nicola Murino <nicola.murino@gmail.com>
Commit-Queue: Nicola Murino <nicola.murino@gmail.com>

ssh/test/session_test.go

@@ -357,11 +357,6 @@ func testOneCipher(t *testing.T, cipher string, cipherOrder []string) {
 
 	numBytes := 4096
 
-	// Exercise sending data to the server
-	if _, _, err := conn.Conn.SendRequest("drop-me", false, make([]byte, numBytes)); err != nil {
-		t.Fatalf("SendRequest: %v", err)
-	}
-
 	// Exercise receiving data from the server
 	session, err := conn.NewSession()
 	if err != nil {
@@ -377,6 +372,11 @@ func testOneCipher(t *testing.T, cipher string, cipherOrder []string) {
 	if len(out) != numBytes {
 		t.Fatalf("got %d bytes, want %d bytes", len(out), numBytes)
 	}
+
+	// Exercise sending data to the server
+	if _, _, err := conn.Conn.SendRequest("drop-me", false, make([]byte, numBytes)); err != nil {
+		t.Fatalf("SendRequest: %v", err)
+	}
 }
 
 var deprecatedCiphers = []string{