abort log tailer for proc during proc shutdown (#811)

Summary:
Pull Request resolved: #811

When proc stops, we shutdown all actors and exit the process. We also join the
log tailers. We need to explicitly abort the log tailers to make sure joining
won't be stuck.

Reviewed By: vidhyav

Differential Revision: D79932041

fbshipit-source-id: 9a19fdcfd9db1f2c2e883288c016a4869fffc3fd

Author: moonli

hyperactor_mesh/src/alloc/process.rs

@@ -473,6 +473,8 @@ impl Alloc for ProcessAlloc {
 
                 Some(Ok((index, mut reason))) = self.children.join_next() => {
                     let stderr_content = if let Some(Child { stdout, stderr, ..} ) = self.remove(index) {
+                        stdout.abort();
+                        stderr.abort();
                         let (_stdout, _) = stdout.join().await;
                         let (stderr_lines, _) = stderr.join().await;
                         stderr_lines.join("\n")