Add ZPOOL device status information in zfsPoolDevStatusTable:

```
SNMP table: BAYOUR-COM-MIB::zfsPoolDevStatusTable

                              zfsPoolDevName zfsPoolDevState zfsPoolDevRead zfsPoolDevWrite zfsPoolDevCksum
                         /var/tmp/zfs_file-1          online              0               0               0
                         /var/tmp/zfs_file-2          online              0               0               0
                         /var/tmp/zfs_file-3          online              0               0               0
 scsi-SATA_VBOX_HARDDISK_VB00c23763-14860ab9          online              0               0               0
 scsi-SATA_VBOX_HARDDISK_VB1f45d95c-477fd9c6          online              0               0               0
 scsi-SATA_VBOX_HARDDISK_VBa23b735b-e12dbf0c          online              0               0               0
 scsi-SATA_VBOX_HARDDISK_VBd15b7714-c746e03e          online              0               0               0
                                     spare-1          online              0               0               0
```