BigSwitch plugin - add portbinding info in requests to controller

Include portbinding info in requests to controller so it receives
information about the compute node like the VIF type and the host
ID. Also includes better debug output on back-end failures.

Fixes: bug #1216061
Change-Id: Ib85c8a088ee9fb94baaf8f28849b318b32d9d672
Merge "BigSwitch plugin - add portbinding info in requests to controller"