Fix possible deadlock in WithProcessKill

We were not checking the error value of `Kill` leading to deadlock if the
process didn't exist.

Signed-off-by: Kenfe-Mickael Laventure <mickael.laventure@gmail.com>

task_opts.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"syscall"
 
+	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/linux/runcopts"
 	"github.com/containerd/containerd/mount"
 )
@@ -33,13 +34,20 @@ type ProcessDeleteOpts func(context.Context, Process) error
 // WithProcessKill will forcefully kill and delete a process
 func WithProcessKill(ctx context.Context, p Process) error {
 	s := make(chan struct{}, 1)
+	ctx, cancel := context.WithCancel(ctx)
+	defer cancel()
 	// ignore errors to wait and kill as we are forcefully killing
 	// the process and don't care about the exit status
 	go func() {
 		p.Wait(ctx)
 		close(s)
 	}()
-	p.Kill(ctx, syscall.SIGKILL)
+	if err := p.Kill(ctx, syscall.SIGKILL); err != nil {
+		if errdefs.IsFailedPrecondition(err) || errdefs.IsNotFound(err) {
+			return nil
+		}
+		return err
+	}
 	// wait for the process to fully stop before letting the rest of the deletion complete
 	<-s
 	return nil