nvmeofgw: added support to nvmeof stretched cluster:

 nvmeofgw: added support to nvmeof stretched cluster:

  GW commands added : set location and set admin state enable/disable
  added start-failback <location> command.

  failover logic is impacted by GW location
  implement GW admin commands  enable/disable
  added map  for location-failback-in-progress
  failback between locations happens only by monitor command
  implemented new ana-group relocation process used
  when inter-location failback command sent
  added upgrade rules

fixes: TODO tracker

Signed-off-by: Leonid Chernin <leonidc@il.ibm.com>