be gentler with terminating tasks which fail to reach STANDBY

If a task fails to report STANDBY state upon startup, we now perform the standard TERM, INT, KILL sequence instead of just KILL.
We also rely on Wait() to close relevant pipes and provide us with exit code.
All above is moved into a dedicated method which will be reused in next fixes.

Author: knopers8

executor/executable/controllabletask.go

@@ -211,25 +211,14 @@ func (t *ControllableTask) doLaunchTask(taskCmd *exec.Cmd, launchStartTime time.
 
 	err = t.pollTaskForStandbyState()
 	if err != nil {
-		t.sendStatus(t.knownEnvironmentId, mesos.TASK_FAILED, err.Error())
-
-		_ = t.rpc.Close()
-		t.rpc = nil
-
-		pid := t.knownPid
-		if pid == 0 {
-			// The pid was never known through a successful `GetState` in the lifetime
-			// of this process, so we must rely on the PGID of the containing shell
-			pid = -taskCmd.Process.Pid
-		}
 		log.WithFields(defaultLogFields).
-			Debug("sending SIGKILL (9) to task")
-		_ = syscall.Kill(pid, syscall.SIGKILL) // fixme: not sure why we do it differently than elsewhere (doTermIntKill)
-		_ = stdoutIn.Close()
-		_ = stderrIn.Close()
+			WithField(infologger.Level, infologger.IL_Support).
+			WithError(err).
+			Error("failed to poll task for standby state")
 
-		log.WithFields(defaultLogFields).
-			Debug("task killed")
+		t.sendStatus(t.knownEnvironmentId, mesos.TASK_FAILED, err.Error())
+
+		t.cleanupFailedTask(taskCmd)
 		return
 	}
 
@@ -314,6 +303,47 @@ func (t *ControllableTask) doLaunchTask(taskCmd *exec.Cmd, launchStartTime time.
 	return
 }
 
+func (t *ControllableTask) cleanupFailedTask(taskCmd *exec.Cmd) {
+
+	defaultLogFields := logrus.Fields{
+		"taskId":    t.ti.TaskID.GetValue(),
+		"taskName":  t.ti.Name,
+		"partition": t.knownEnvironmentId.String(),
+		"detector":  t.knownDetector,
+	}
+
+	if taskCmd.Process == nil {
+		// task never started or was already terminated
+		return
+	}
+
+	if t.rpc != nil {
+		_ = t.rpc.Close()
+		t.rpc = nil
+	}
+
+	pid := t.knownPid
+	if pid == 0 {
+		// The pid was never known through a successful `GetState` in the lifetime
+		// of this process, so we must rely on the PGID of the containing shell
+		pid = -taskCmd.Process.Pid
+	}
+
+	_ = t.doTermIntKill(-taskCmd.Process.Pid)
+
+	err := taskCmd.Wait()
+	if err != nil {
+		log.WithFields(defaultLogFields).
+			WithField(infologger.Level, infologger.IL_Support).
+			WithError(err).
+			Warning("task terminated and exited with error")
+	} else {
+		log.WithFields(defaultLogFields).
+			WithField(infologger.Level, infologger.IL_Support).
+			Debug("task terminated")
+	}
+}
+
 func (t *ControllableTask) initTaskStdLogging(stdoutIn io.ReadCloser, stderrIn io.ReadCloser) {
 	defaultLogFields := logrus.Fields{
 		"taskId":    t.ti.TaskID.GetValue(),