crosvm: cros_async: disable unstable test

Test verifies if operation is not executed if executor is dropped before
running. We do not currently guarantee that

BUG=none
TEST=cargo test

Change-Id: I56d98e4af869c26542c7ebacb127ed3bfd980553
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3655277
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Commit-Queue: Anton Romanov <romanton@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>

cros_async/src/sys/unix/uring_executor.rs

@@ -1110,6 +1110,8 @@ mod tests {
             .expect("Failed to run executor");
     }
 
+    // We will drain all ops on drop and its not guaranteed that operation won't finish
+    #[ignore]
     #[test]
     fn drop_before_completion() {
         if !use_uring() {