update packngo to 0.5.1

[displague]

Fixes #38

With this update, the provider will access the "api.equinix.com/metal/v1" API instead of "api.packet.net"

Setting and getting NetworkType for a device is done more explicility through DevicePort and helper functions.

Signed-off-by: Marques Johansson mjohansson@equinix.com

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