Why non-root users being prompted for the polkit authentication in ssh session?

Issue

• Why below error is occurring in ssh session?

  root@localhost:/) ssh -l user example.com
  user@example.com's password:
  Last login: Mon May 22 19:03:58 2017
  setenforce:  setenforce() failed
  ==== AUTHENTICATING FOR org.freedesktop.systemd1.manage-units ===
  Authentication is required to manage system services or units.
  Authenticating as: root
  Password:
  polkit-agent-helper-1: pam_authenticate failed: Authentication failure
  ==== AUTHENTICATION FAILED ===
  Failed to stop firewalld.service: Access denied
  See system logs and 'systemctl status firewalld.service' for details.
  $