NetworkProtocol: Support NetworkSuppliedServers property

There was no way to differentiate between the static and DHCP assigned
NTP servers. Networkd and Dbus has added support for StaticNTPServers to
save the static configuration.

PATCH command will now set the StaticNTPServers property at the backend.
NTPServers property will contain network supplied dynamic NTP Servers at
the system.

Tested by:
 1. PATCH /redfish/v1/Managers/bmc/NetworkProtocol -d
    '{"NTP":{"NTPServers": [<ip>]}}'
    Verify that this adds the NTPs server to the NetworkProtocol
 2. Enable DHCP to fetch NTP servers list from the DHCP server. Verify
    that they are listed when GET on NetworkProtocol as below
    "NTP": {
        "NTPServers": [
        <static ntp server ip>
      ],
      "NetworkSuppliedServers": [
        <dynamic ntp server ip>
      ],
      "ProtocolEnabled": true
    },
 3. Redfish validator run

Signed-off-by: sunharis <sunithaharish04@gmail.com>
Change-Id: Ifac77485485839292b770d36def35da17d723c4e