do_stop() in systemv.sh function doesn't kill child processes of the service process

Currently, I have added following lines in the beginning of do_stop() function to get around this issue - 
```bash
SERVICEPID = $(pgrep -f -o "{{{project.artifactId}}}")
pkill -P $SERVICEPID
```
I can create a pull request if you find this correct. Also, if you think this is not an issue and there is some mistake on my part, please do tell.