Plugin does not work in 4.9.0

[snyrkill]

The plugin works fine in Rundeck 4.8.0 but does not load in 4.9.0 snapshot.

[akh13]

I've been experimenting on a few installations, and submitted #8 to address what I think this might be. It worked just fine until an update to 4.9.0, then it broke. These changes got it working again, but I would definitely appreciate a second set of eyes if someone wishes to confirm.

[akh13]

Plugin confirmed to work with 4.11.0 with the above, but with a lot of jobs, it does take some time to display the graph (~5s).

[snyrkill]

This works now, thank you.