Update spki_table_add_entry and spki_table_get_all.

- spki_table_add_entry
	- Remove free call -> leave this task to the user.
	  The delivered memory could also be on the stack.

- spki_table_get_all
	- Change signature to allow passing back error codes
	- Add check for ASN and SKI because the hash lib not
	  guarantee to pass back only elemnts matching the given hash.
	- Copy result to new memory because the data could change
	  while the user is working with it
	- Hold lock until the end because the hash table could be
	  changed by other threads while building the result.