test_interface: negotiate_auto platform fixes
test_interface: negotiate_auto platform fixes

* This was mostly solved by simply setting a speed value before trying to change the negotiate auto settings.
* Note that negotiate is not supported on 10G and larger interfaces
* Tested on n3-i2,n3-i3,n5,n6,n7(skips),n8,n9

cisco/cisco-network-node-utils,cisco/cisco-network-node-utils,chrisvanheuveln/cisco-network-node-utils,chrisvanheuveln/cisco-network-node-utils