[ssh] change check for ssh_server_policies.

scripts/hostcfgd

@@ -1354,7 +1354,7 @@ class PamLimitsCfg(object):
 
     # Read max_sessions config
     def read_max_sessions_config(self, ssh_server_policies):
-        if ssh_server_policies is not None:
+        if not ssh_server_policies:
             max_sess_cfg = ssh_server_policies.get('max_sessions', 0)
             self.max_sessions = max_sess_cfg if max_sess_cfg != 0 else None