switch monc, daemons to use new msgr2 auth frame exchange

switch monc, daemons to use new msgr2 auth frame exchange

- MonClient implements AuthClient to authenticate as a client
- MonClient implements AuthServer to allow daemons to verify authorizers
- Monitor implements AuthServer to allow clients to authenticate with
  an exchange of msgr2 frames
- Monitor implements AuthClient to authenticate with other monitors

After this change ProtocolV1 and SimpleMessenger still use all of the
old Dispatcher-based callbacks, but ProtocolV2 doesn't need them at
all (except for ms_handle_authentication when we finish).

Signed-off-by: Sage Weil <sage@redhat.com>