main/openssh: sshd.pam and sshd.krb5 binary selection logic doesn't check sshd_config.d/*

With 3903cd46 , users can decide to put the UsePAM yes directive in /etc/ssh/sshd_config.d/whatever.conf instead of /etc/ssh/sshd_config. However /etc/init.d/sshd only looks in the latter so it ends up launching the default sshd that doesn't have PAM support. This is easily noticeable from the resuling log:

auth.info sshd[9310]: /etc/ssh/sshd_config.d/99-overrides.conf line 9: Unsupported option UsePAM

The get_conf function there needs to be changed to consider all files in the directory too, following the same logic openssh uses for Include (multiple files are processed in lexical order, last directive wins).