fix(jungle): change pid existence check's condition branches

[adam101]

Pull request #1545 broke the ability to stop and restart running instances. The old version of checking $PID existence was truthy on non-existence, now it's truthy on existence.

Example in case of existing PID 1209:

$ if [ "`ps -A -o pid= | grep -c 1209`" -eq 0 ]; then echo true; else echo false; fi;
true

$ if ps -p 1209 > /dev/null; then echo true; else echo false; fi;
false

[p8]

This fixes an issue we had with stopping and restarting. 👍