[tests] kill child processes on exit

It looks like some child processes weren't being killed at the end of
tests, leaving them hanging forever. Fix that by killing them at the end
of the test.

Detected by the new test runner I'm writing.

Closes: aptos-labs#7970

consensus/safety-rules/tests/binary.rs

@@ -34,9 +34,17 @@ fn test_consensus_state() {
         .stdin(std::process::Stdio::inherit())
         .stdout(std::process::Stdio::inherit())
         .stderr(std::process::Stdio::inherit());
-    command.spawn().unwrap();
+    let mut child = command.spawn().unwrap();
 
     let safety_rules_manager = SafetyRulesManager::new(&config);
     let mut safety_rules = safety_rules_manager.client();
-    safety_rules.consensus_state().unwrap();
+    let consensus_state = safety_rules.consensus_state();
+
+    // Ensure the safety-rules subprocess is killed whether the test passes or fails.
+    // Not doing this would result in a zombie process.
+    child.kill().expect("could not kill safety-rules process");
+    child
+        .wait()
+        .expect("could not wait on safety-rules process");
+    consensus_state.unwrap();
 }

execution/execution-correctness/tests/binary.rs

@@ -27,11 +27,18 @@ fn test_rest() {
         .stdin(std::process::Stdio::inherit())
         .stdout(std::process::Stdio::inherit())
         .stderr(std::process::Stdio::inherit());
-    command.spawn().unwrap();
+    let mut child = command.spawn().unwrap();
 
     // Run a command as a client to verify the service is running
-    ExecutionCorrectnessManager::new(&config)
-        .client()
-        .reset()
-        .unwrap();
+    let res = ExecutionCorrectnessManager::new(&config).client().reset();
+
+    // Ensure the safety-rules subprocess is killed whether the test passes or fails.
+    // Not doing this would result in a zombie process.
+    child
+        .kill()
+        .expect("could not kill execution-correctness process");
+    child
+        .wait()
+        .expect("could not wait on execution-correctness process");
+    res.unwrap();
 }