Ignore failed tasks by default
Ignore failed tasks by default

Recently, there are a lot of these Docker transient errors when spawning
the first task:

"Failed to run docker container: User defined networks require Docker version 1.9.0 or higher"

This is not consistent and it's happening only when trying to spawn
the first task, while second one will work.

ionutbalutoiu/mesos-jenkins,ionutbalutoiu/mesos-jenkins