Baremetal server can't get correct TFTP server address for provisioning

Contrail sets 'siaddr' field in DHCP reply to address of TSN node. According to rfc2131 https://www.ietf.org/rfc/rfc2131.txt 'siaddr' is recognized by PXE client as tftp server to boot from, even when option 66 tftp-server-name is set. The good explanation of 'siaddr' field is in https://tools.ietf.org/html/rfc5859

It leads to failed deployment of Baremetal node which doesn't support IPXE. IPXE doesn't use 'siaddr' or option 66. It use only option 67 - which is direct http or ftp link.

An example of DHCP reply from Contrail (both Server-IP 'siaddr' and Server-ID 'option 54 are set to the TSN node 10.20.30.2)

    10.20.30.2.67 > 255.255.255.255.68: [no cksum] BOOTP/DHCP, Reply, length 326, xid 0x7a6c69a8, Flags [Broadcast] (0x8000)
          Your-IP 10.20.30.82
          Server-IP 10.20.30.2
          Client-Ethernet-Address 0c:c4:7a:6c:69:a8
          Vendor-rfc1048 Extensions
            Magic Cookie 0x63825363
            DHCP-Message Option 53, length 1: Offer
            Server-ID Option 54, length 4: 10.20.30.2
            Lease-Time Option 51, length 4: 4294967295
            Subnet-Mask Option 1, length 4: 255.255.255.0
            BR Option 28, length 4: 10.20.30.255
            BF Option 67, length 11: "/pxelinux.0"
            T210 Option 210, length 18: 12150,24946,12140,26978,12148,26228,28770,28527,29743
            TFTP Option 66, length 11: "10.20.30.11"
            Default-Gateway Option 3, length 4: 10.20.30.1
            Domain-Name-Server Option 6, length 4: 10.20.30.2