Only change interface type if actually changing speed
Only change interface type if actually changing speed

Summary: Keep port flaps to a minimum

Reviewed By: aeckert

Differential Revision: D3968862

fbshipit-source-id: 6022247d3bc6c612febc5ed0bddc774ab4f9a66a

peterlei/fboss,peterlei/fboss,peterlei/fboss,peterlei/fboss