I'm running CentOS 7.2; see below:
# systemctl stop firewalld
Error getting authority: Error initializing authority: Error calling StartServiceByName for org.freedesktop.PolicyKit1: Timeout was reached (g-io-error-quark, 24)
Failed to stop firewalld.service: Connection timed out
Failed to get load state of firewalld.service: Connection timed out
journalctl just reports the following error: [system] Failed to activate service 'org.freedesktop.PolicyKit1': timed out
I found this bug for Ubuntu and a possible related one for a RHEL 7 bug.