crypto/ssh: fix format string error in test.

Change-Id: I0c84f11fb74ee478617deb1b743a759c9f789101
Reviewed-on: https://go-review.googlesource.com/10822
Reviewed-by: Adam Langley <agl@golang.org>

ssh/cipher_test.go

@@ -120,7 +120,7 @@ func TestCBCOracleCounterMeasure(t *testing.T) {
 		}
 
 		if i > 0 && bytesRead != lastRead {
-			t.Errorf("corrupt byte %d: want %d, got %d bytes read", bytesRead, lastRead)
+			t.Errorf("corrupt byte %d: read %d bytes, want %d bytes read", i, bytesRead, lastRead)
 		}
 		lastRead = bytesRead
 	}