pgbouncer: Ensure pgbouncer service is enabled

[vitabaks]

Issue: https://github.com/vitabaks/postgresql_cluster/issues/452

• Stop and disable init script only if there is no systemd file

  • Now we first check if the pgbouncer systemd service file exists. If it does not exist, then we stop and disable the service, assuming that it is managed via init script.

• Ensure pgbouncer service is enabled

[vitabaks]

root@pgnode01:/# systemctl status pgbouncer
● pgbouncer.service - pgBouncer connection pooling for PostgreSQL
     Loaded: loaded (/etc/systemd/system/pgbouncer.service; enabled; vendor preset: enabled)
     Active: active (running) since Wed 2023-08-30 13:38:20 UTC; 24min ago
   Main PID: 15036 (pgbouncer)
      Tasks: 2 (limit: 77073)
     Memory: 2.3M
        CPU: 231ms
     CGroup: /docker/f7d5a4e8f03fb3bd414fd675ab6408af5c4f3082fc2a0f60e7676a9975f3a0c2/system.slice/pgbouncer.service
             └─15036 /usr/sbin/pgbouncer -d /etc/pgbouncer/pgbouncer.ini

Aug 30 13:38:19 pgnode01 systemd[1]: Starting pgBouncer connection pooling for PostgreSQL...
Aug 30 13:38:19 pgnode01 systemd[1]: pgbouncer.service: Can't open PID file /run/pgbouncer/pgbouncer.pid (yet?) after start: Operation not permitted
Aug 30 13:38:20 pgnode01 systemd[1]: Started pgBouncer connection pooling for PostgreSQL.

• enabled