[PATCH] replication: improve join/subscribe logging

[Vladimir Davydov]

On Thu, Feb 14, 2019 at 08:44:36PM +0300, Vladimir Davydov wrote:
> This patch makes logging a little bit more verbose so as to facilitate
> post-mortem replication failure analysis:
> 
>  - When an instance starts up, print its uuid and vclock.
>  - When a replica connects to a master, print the master's uuid.
>  - Log join/subscribe events in the master's log; print replica uuid,
>    address, and vclock.

Come to think of it, we also need to print id assigned to
each replica, otherwise vclocks wouldn't make much sense.
I'll patch replica_{set,clear}_id in v2.

Also, we should probably be more verbose in applier as well
and print local and remote vclocks when an applier subscribes.
Will do it, too.