Fixes

This fixes a bug in the recent roles commit (59f124e162335df696a56e65a4272390fbf9146f).  It also adds a minor fix for cases where sometimes offers aren't declined, even though they should be.

In order for this to build, the Mesos 0.14.0 jar must be up-to-date with current Mesos master.

@florianleibert @andykram