Ticket 517 - crash in DNA if no dnaMagicRegen is specified
Bug Description: There are several places where we deference config_entry->generate
Fix Description: Properly check for NULL, and allow the update of dnaType.
https://fedorahosted.org/389/ticket/517
Reviewed by: richm(Thanks Rich)
(cherry picked from commit d97835969db3e957032c52ac317699354299c07c)