network_id may not be specified in a port-update request. Read if from port_obj in that case.

Change-Id: Iff88bc9a19d7351fb8dd027497154a4eee380bf4
Closes-Bug: 1358212
(cherry picked from commit 01ae1582be1e5c99a47627e5532005f76f2e5821)
Merge "network_id may not be specified in a port-update request. Read if from port_obj in that case." into R1.10