tree-expand-promise unit test cleanup
tree-expand-promise unit test cleanup

* Fix typos and assertion phrasing
* Clean out unnecessary this.async usage
* Suppress dgrid-error logging by canceling event

kfranqueiro/dgrid,maier49/dgrid,maier49/dgrid,dylans/dgrid,kfranqueiro/dgrid,dylans/dgrid,maier49/dgrid,dylans/dgrid,kfranqueiro/dgrid