Failed to retrieve hv.datastore.latency item when multiple datastores with duplicate name are mounted on hv.

Environment:

Several hypervisors are managed by a vCenter, one datastore is mounted on each hypervisors with same datastore name.

                |-- hv1 --|
vCenter -|-- hv2 --|- datastoreA
                |-- hv3 --|

Problem:

Zabbix default vmware template discover 3 datastore on each hypervisor host, but only one hv.datastore.latency item can work, others become not supported with the error below.

Unknown hypervisor "HYPERVISOR NAME" for datastore "DATASTORE NAME"

The problem doesn't happen if datastore name are different, like:

hv1 - datastoreA-1 --|
hv2 - datastoreA-2 --|- datastoreA
hv3 - datastoreA-3 --|

There was no problem on Zabbix 2.2 with same datastore name, problem happens on 4.0.

Also, latency information in datastore.read and datastore.write of vCenter host are calculated by Zabbix server from total latency value of hypervisor, so latency item on vCenter host is incorrect, it uses only one hv.datastore.latency item value.