Adds `confluentdbutil showattrib <noderange> <attribute>...` to print the
node attribute.
In contrast to nodeattrib it can shows secrets and crypted values with -u flag.
It's server-side only: reads the config store and master key directly, never over
the API.
It's read-only and works without confluentd running.
Markus Hilger
Jarrod Johnson
vmaneagit