Add new interface Config variables added to Nexus plugin.
vnc_pool
intfcfg.portchannel
Identify variables which are obsolete and those being deprecated.
Change default to switch_heartbeat_time.
Depends-On: I940659bdd448b7bda1c38d9343ec6322390b027a
Change-Id: I1995711fc976e72e4254fc0738e4c91b455830ab
Closes-bug: #1672493