Zabbix

........S. [ZBXNEXT-3480] update the inventory data in cache on the fly

For having always updated data in cache, we update the
inventory data in configuration cache during history
synchronization.
The configuration cache update will happen after the new
inventory data are persisted in the database and in case
an host inventory is not present in configuration cache,
we update only the database data and let the global
configuration cache synchronization procedure load the
missing inventories from the database.

For properly linking the inventory updates with the
inventory structure in cache, a new "link" field was added
to the zbx_inventory_value_t structure.
The field will keep track of the integer index for finding the
correct string in the host inventory structure "fields" array
to update.

The new DCconfig_update_inventory_values() function
will take care of locking the cache and updating the
necessary inventory structures in configuration cache.