Add "network agent set" command in network v2 to set network
agent properties.
Also add the unit test, doc, functional test and release note.
Change-Id: Iebaee4c60f8c6b43f538c1b82a38b93178b9ce53
Implements: bp implement-network-agents
Co-Authored-By: Michael Gugino <michael.gugino@walmart.com>