internal/runner: recover on panic, fail task

This makes sure the task is not left in an active state if the task
handlers panic. Going ahead I'd like to move this into the controller library, for
now this can be here.

internal/runner/runner.go

@@ -2,6 +2,7 @@ package runner
 
 import (
 	"context"
+	"runtime/debug"
 	"time"
 
 	"github.com/metal-toolbox/flasher/internal/model"
@@ -66,6 +67,15 @@ func (r *Runner) RunTask(ctx context.Context, task *model.Task, handler Handler)
 		return nil
 	}
 
+	defer func() error {
+		if rec := recover(); rec != nil {
+			r.logger.Printf("!!panic %s: %s", rec, debug.Stack())
+			r.logger.Error("Panic occurred while running task")
+			return taskFailed(errors.New("Task fatal error, check logs for details"))
+		}
+		return nil
+	}() // nolint:errcheck // nope
+
 	// no error returned
 	_ = task.SetState(model.StateActive)
 	handler.Publish()