feat: replace systemctl commands with service equivalents

for sake of installing to devuan instead of debian, although the
latter should still work okay iiuc..

rattail_fabric2/postgresql.py

@@ -93,14 +93,14 @@ def restart(c):
     """
     Restart the PostgreSQL database service
     """
-    c.sudo('systemctl restart postgresql.service')
+    c.sudo("service postgresql restart")
 
 
 def reload_(c):
     """
     Reload config for the PostgreSQL database service
     """
-    c.sudo('systemctl reload postgresql.service')
+    c.sudo("service postgresql reload")
 
 # TODO: deprecate / remove this
 reload = reload_