server: Don't call _assuan_waitpid on server side.

* src/server.c (_assuan_server_finish): Never call waitpid here.
* src/assuan-socket-server.c (accept_connection_bottom): Indentation.

The waitpid/wait only makes sense by parent catching its child
process.

Since the commit 93595de1ede96dedfcaa93c7442536a2cde0b6ef (for version
0.6.5, in 2004-04-21), CTX->PID on server side has client PID.

In the commit cb53f862ff2a864da822d1c16d3df6a02157608b (2009-11-19),
call of _assuan_waitpid was introduced in assuan_server_finish, but
this call always fails because the process is not a child process of
server.

(If we could catch exit of non-child process, it might cause a dead
lock, since client does call waitpid too.)

The indentation fix is to show the place where PID is assigned.

• Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>