try builds on Servo flood Buildbot

[Manishearth]

We tried @bors-servo: try on servo/servo#6244, and buildbot was queued up with around 200 PRs starting around January (all on the try branch).

Our config: https://github.com/servo/saltfs/blob/master/homu/cfg.toml (buildbot config

Some example builds: http://build.servo.org/builders/mac2/builds/2106 , http://build.servo.org/builders/mac2/builds/2107 , http://build.servo.org/builders/mac2/builds/2108 , http://build.servo.org/builders/mac2/builds/2109

Did we do something wrong here? Is this a homu bug?

cc @larsbergstrom @edunham

[alexcrichton]

This used to happen to us in Rust, and we ended up just setting a higher treeStableTimer option when making the schedulers (maybe relevant?)