Re: allow online change primary_conninfo

Hi

> I don't quite think this is the right design. IMO the startup process
> should signal the walreceiver to shut down, and the wal receiver should
> never look at the config.

Ok, i can rewrite such way. Please check attached version.

> Otherwise there's chances for knowledge of
> pg.conf to differ between the processes.

I still not understood why this:
- is not issue for startup process with all primary_conninfo logic
- but issue for walreceiver with Michael Paquier patch; therefore without any primary_conninfo change logic in startup.
In both cases primary_conninfo change logic is only in one process.

regards, Sergei