Remove the deprecated -nodefconfig option

It's the same as -no-user-config and marked as deprecated since three
releases already. Time to remove it now.

Acked-by: Peter Krempa <pkrempa@redhat.com>
Acked-by: Ján Tomko <jtomko@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>