Add physical_network to binding:vif_details dictionary

During port binding binding:vif_details dictionary is
updated with physical_network to be used by mlnx nova vif driver.
binding:profile update will be removed once nova side fix is merged
to keep consistent solution.

Change-Id: If9525929a1546e8d05f7923570d30dfc2eed8898
Closes-Bug: 1304872
Merge "Add physical_network to binding:vif_details dictionary"