I had this same issue in current version after installing SSL through the ssl manager in Apache section.
The server could not stop httpd, and it was still running fine, it seemed.
Just trying to kill httpd processes, the server would just spawn a new process. Rebooting seemed to fix the problem.
However, without rebooting, I could use a combination of the advice above to get it working properly again:
killall -9 httpd && service httpd restart
Somehow running the commands separately would not do it. (Makes no sense I know...)