FIX: use /sbin/nologin for service accounts

These accounts existed only for container UID mapping and filesystem
ownership, but user.present omitted shell:, so Salt fell through to the
platform useradd default and every one of them got /bin/bash. Pin them to
/sbin/nologin so none can be used as an interactive login or `su -` target.

socore keeps /bin/bash: `su socore -c '/usr/sbin/so-repo-sync'` in soup and
so-kernel-upgrade execs the account's passwd shell, and operator docs tell
users to su to socore. soqemussh keeps /bin/bash as an SSH login account.

elastic-agent, elastic-agent-pr and kafka are included alongside the accounts
named in the issue, being the same class with the same unset shell, so the
default is uniform.

Cron is unaffected: cronie runs jobs via the crontab SHELL (default /bin/sh),
not the passwd shell. suricata is the only account changed here that owns a
crontab, and somon has shipped as nologin with a working cron job already.
The zeek `runuser -l zeek` calls all run inside so-zeek via docker.run/exec,
so they resolve the shell from the image, not the host.

Verified on a 3.4.0 managersearch + sensor grid: highstate converges with the
shell as the only change and no failures, is idempotent on a second run, all
containers stay up, SOC still issues a Kratos login flow, and the suricata
surilogcompress cron job runs post-change ((suricata) CMD/CMDEND in
/var/log/cron) while `su - suricata` is now refused.

Closes #16256

salt/elastalert/config.sls

@@ -21,6 +21,7 @@ elastalert:
     - gid: 933
     - home: /opt/so/conf/elastalert
     - createhome: False
+    - shell: /sbin/nologin
 
 elastalogdir:
   file.directory:

salt/elastic-fleet-package-registry/config.sls

@@ -19,6 +19,7 @@ elastic-agent-pr:
     - gid: 948
     - home: /opt/so/conf/elastic-fleet-pr
     - createhome: False
+    - shell: /sbin/nologin
 
 {% else %}
 

salt/elasticagent/config.sls

@@ -20,6 +20,7 @@ elastic-agent:
     - gid: 949
     - home: /opt/so/conf/elastic-agent
     - createhome: False
+    - shell: /sbin/nologin
 
 elasticagentconfdir:
   file.directory:

salt/elasticfleet/config.sls

@@ -26,6 +26,7 @@ elastic-fleet:
     - gid: 947
     - home: /opt/so/conf/elastic-fleet
     - createhome: False
+    - shell: /sbin/nologin
 
 elasticfleet_sbin:
   file.recurse:

salt/elasticsearch/config.sls

@@ -32,6 +32,7 @@ elasticsearch:
     - gid: 930
     - home: /opt/so/conf/elasticsearch
     - createhome: False
+    - shell: /sbin/nologin
 
 elasticsearch_sbin:
   file.recurse:

salt/kafka/config.sls

@@ -21,6 +21,7 @@ kafka_user:
     - gid: 960
     - home: /opt/so/conf/kafka
     - createhome: False
+    - shell: /sbin/nologin
 
 kafka_home_dir:
   file.absent:

salt/kibana/config.sls

@@ -22,6 +22,7 @@ kibana:
     - gid: 932
     - home: /opt/so/conf/kibana
     - createhome: False
+    - shell: /sbin/nologin
 
 # Drop the correct nginx config based on role
 

salt/kratos/config.sls

@@ -27,6 +27,7 @@ kratos:
     - uid: 928
     - gid: 928
     - home: /opt/so/conf/kratos
+    - shell: /sbin/nologin
 
 kratosdir:
   file.directory:

salt/logstash/config.sls

@@ -35,6 +35,7 @@ logstash:
     - uid: 931
     - gid: 931
     - home: /opt/so/conf/logstash
+    - shell: /sbin/nologin
 
 logstash_sbin:
   file.recurse:

salt/suricata/config.sls

@@ -64,6 +64,7 @@ suricata:
     - gid: 940
     - home: /nsm/suricata
     - createhome: False
+    - shell: /sbin/nologin
 
 socoregroupwithsuricata:
   group.present:

salt/zeek/config.sls

@@ -23,6 +23,7 @@ zeek:
     - gid: 937
     - home: /opt/so/conf/zeek
     - createhome: False
+    - shell: /sbin/nologin
 
 # Create some directories
 zeekpolicydir: