Make NnfSystemStorage easier to manage when Rabbits are disabled/enabled

[matthew-richerson]

When creating new storage on the Rabbits, the NnfSystemStorage does not create storage on Rabbits that are disabled. When they transition to enabled the NnfSystemStorage controller will create storage on them. However, this does not work if there were any Rabbits that had previously been enabled that are now disabled. Change this behavior so that the NnfSystemStorage ignores Rabbits that are disabled, even if they had been previously enabled.