Description of problem:
Original bug reporter submitted:  
I've noticed a very strange behaviour which resulted in me not having a firewall running for quite a few hours. 
If I run:
"systemctl reload firewalld"
firewalld stops instead of being reloaded.
The console doesn't return a message and it all looks like the reload action is carried out successfully.
Indeed, my earlier command had stopped firewalld altogether!
I've reproduced this behaviour all the time.

Version-Release number of selected component (if applicable):
7.1-1503, 7.2-1511

How reproducible:
Always

Steps to Reproduce:
1. Check firewalld is running with "systemctl status firewalld". Result: active
2. Run "systemctl reload firewalld"
3. Check firewalld is running with "systemctl status firewalld". Result: active
4. Run "systemctl reload firewalld"
5. Check status with "systemctl status firewalld". Result is: inactive

Actual results:
firewalld exits after the 2nd SIGHUP because the signal handler is not set back up after the 1st time it is handled

Expected results:
Upon SIGHUP, firewalld should execute the firewall reload and set the SIGHUP signal handler back up 

Additional info:
I resolved this issue within the CentOS Bug Tracker under bug 9054 (https://bugs.centos.org/view.php?id=9054) and was told I needed to submit the bug and fix here.