Problem description: If during the same host update a template is unlinked and its items are cleared and then the template is added back again, the items that belong to this template are re-created on the host (they have new ids). In this case the items loose all of their history records. It is expected that if templated is unlinked and cleared and the linked again during the same host update, the entries (items, triggers, graphs...) that correspond to this template stay unchanged.

Steps to reproduce:

1. Open configuration of any host that has a linked template
2. Open DB and check the ids of the items that are inherited by this host from the template
3. Perform the unlink and clear action for this template on the host but don't update host configuration yet
4. Link the template back to this host
5. Update host configuration
6. Check the ids of the items that are inherited by this host from the template

Result: the ids of items are changed, which means that the items are re-created and that they've lost all of their history records
Expected: in the above described scenario the items and other entries inherited by the host from this template should remain unchanged