* Currently, objects created in preset are never deleted.
k6 deletes only objects from registry, if registry file
is not provided k6 delete load fails.
* Changed delete scenarios so they check if registry was
provided and if it is not empty, and if not, they try
deleting objects created in preset.
Signed-off-by: Ekaterina Lebedeva <ekaterina.lebedeva@yadro.com>
