do not set UsePAM on OpenBSD

Upstream opensshd does not support PAM

openssh/files/sshd_config

@@ -134,6 +134,7 @@
 
 {{ option_default_uncommented('Subsystem', 'sftp /usr/lib/openssh/sftp-server') }}
 
+{% if not salt['grains.get']('os') == 'OpenBSD' -%}
 # Set this to 'yes' to enable PAM authentication, account processing,
 # and session processing. If this is enabled, PAM authentication will
 # be allowed through the ChallengeResponseAuthentication and
@@ -144,6 +145,7 @@
 # PAM authentication, then enable this but set PasswordAuthentication
 # and ChallengeResponseAuthentication to 'no'.
 {{ option_default_uncommented('UsePAM', 'yes') }}
+{%- endif %}
 
 # DNS resolve and map remote IP addresses
 {{ option('UseDNS', 'yes') }}