A fix fog gh-452 crash hot_standby test

Recovery now needs to be run in a non-sched fiber.
Create a fiber for it in on_bind callback.

On another token:

- rename snap_daemon to snapshot_daemon
- don't output redundant snap_daemon prefix in the log, it's already
in the fiber name.
- miscallenous cleanups (roles).
Merge branch 'master' of github.com:tarantool/tarantool