Add /etc/ssh/sshd_config.d to the file list

This is a bit of a mess: sshd can only load configuration from
/etc/ssh/sshd_config.d, and that directory is declared as non-world-readable.
This is in violation of the packaging guidelines which say that packaged files
must be world-readable, and also makes very little sense, since those files
are part of the package payload.

If we create the directory with different permissions, and list it in %files,
installation will fail. If we don't list it in %files, and the user doesn't have
openssh-server installed, they will have an unowned directory. Another option
would be to depend on owner of this directory, i.e. openssh-server, but we don't
want to have that dependency. So let's copy the %files line from openssh-server
and figure out what to do if it changes in openssh-server again.

split-files.py

@@ -8,6 +8,7 @@ known_files = '''
 %ghost %attr(0444,root,root) /etc/udev/hwdb.bin
 /etc/inittab
 /usr/lib/systemd/purge-nobody-user
+%dir %attr(0700,root,root) /etc/ssh/sshd_config.d
 %ghost %config(noreplace) /etc/vconsole.conf
 %ghost %config(noreplace) /etc/X11/xorg.conf.d/00-keyboard.conf
 %ghost %attr(0664,root,root) %verify(not group) /run/utmp