mon/AuthMonitor: add dump-keys and wipe-rotating-service-keys

mon/AuthMonitor: add dump-keys and wipe-rotating-service-keys

`auth dump-keys` allows examining the key types for each entity and also the
rotating session keys. This lets us confirm key upgrades are done as expected.

`wipe-rotating-service-keys` clears out existing non-auth service keys so that we do not
need to wait for the rotating key expiration. It is not disruptive so long as clients
renew their tickets when prompted by the auth epoch change.

Signed-off-by: Patrick Donnelly <pdonnell@ibm.com>