Attempt to make GN waterfall bots not on the CQ alert but not close trees.
Attempt to make GN waterfall bots not on the CQ alert but not close trees.

I think that if we make all of the steps on the GN bots non-closing, 
that will keep them from closing the tree, but the events will 
still propagate through to sheriff-o-matic.

R=stip@chromium.org, seanmccullough@chromium.org
BUG=497970

Review URL: https://codereview.chromium.org/1703353002

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@299395 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build