The host config_target is taken as a snapshot on the upgrade-start.
This can lead to config out of date condition if the N controller
issues subsequent config requests. This is more likely in duplex
controllers, however, for consistency the config_target is reset
to track when the N+1 controller is active.
Clear the config target of all hosts on upgrade migration. The N+1
controller will resume tracking the config by generating config_target
when configuration is issued.
Condition for upgrade activation-complete is updated to account
for potential None config_target.
Verified upgrade complete on AIO-SX and Duplex systems.
Signed-off-by: John Kung <firstname.lastname@example.org>