[Nmh-workers] specifying SMTP server in mts.conf broken by TLS certificate changes

[Oliver Kiddle]

With a build from current git, post seg faults for me.
I've bisected this down to 5cb3431b (Add support for certificate
verification when using TLS).

New code in smtp_init() is assuming that the server parameter is a string
containing the SMTP server. It isn't unless you specify -server as a
switch to post. If you have the server configured in mts.conf, it is
still NULL at this point. smtp_init goes on to call rclient() which is a
wrapper around client().

client()'s first parameter (args) is this server switch and it checks
whether it is NULL to determine whether it is used. Otherwise it takes
the global variable servers, which was filled in when mts.conf was
parsed, splits it into words and then there's a for loop as it trys to
connect to the servers in turn.

So I'm guessing that much of the new code added in 5cb3431b should be
moved from smtp_init() into client().

I think there may be other problems predating 5cb3431b too. When
bisecting, I was getting the following error for earlier commits:
  post: problem initializing server; [BHST] no servers available
I've not looked further into that.

Oliver