Fix Selenium not starting.

[fengtan]

Thanks for this great script.
This error seems to show up when starting the service:

[user@workstation ~]$ /etc/init.d/headless-selenium start
Starting Xvfb...
Starting Selenium.
Error 0! Couldn't start Selenium!
Stopping Headless Selenium...

On my machine, at line 137 I have $num = 3 which does not seem to indicate that there is a problem.
Here is an attempt to fix the issue. Does it make sense ?

[larsen0815]

Worked for me with selenium-server-standalone-3.7.1.jar