Work around podman bug in api/image_exists

It should be fixed in podman 3 via
containers/podman@3fa61f0

api/image_exists.go

@@ -22,5 +22,8 @@ func (c *API) ImageExists(ctx context.Context, nameWithTag string) (bool, error)
 	if res.StatusCode == http.StatusNoContent {
 		return true, nil
 	}
+	if res.StatusCode == http.StatusInternalServerError {
+		return true, nil
+	}
 	return false, fmt.Errorf("unknown error, status code: %d", res.StatusCode)
 }

driver.go

@@ -477,7 +477,9 @@ func (d *Driver) StartTask(cfg *drivers.TaskConfig) (*drivers.TaskHandle, *drive
 		// do we already have this image in local storage?
 		haveImage, err := d.podman.ImageExists(d.ctx, createOpts.Image)
 		if err != nil {
-			return nil, nil, fmt.Errorf("failed to start task, unable to check for local image: %v", err)
+			// we assume that we do NOT have a local image if something goes wrong
+			// it could work to pull/start a container
+			d.logger.Warn("failed to check for local image", "image", createOpts.Image, "err", err)
 		}
 		if !haveImage {
 			// image is not in local storage, so we need to pull it