Use proto enums rather than commented literal ints
Use proto enums rather than commented literal ints

Summary:
We have named values for these, might as well use them.
For reference: https://github.com/apache/mesos/blob/3dd75134b8006fda0238ebe97634cca941769e66/include/mesos/mesos.proto#L514

Test Plan: None

Reviewers: nate, paulruan

Reviewed By: paulruan

Subscribers: changesbot

Differential Revision: https://tails.corp.dropbox.com/D157375

dropbox/changes-mesos-framework,dropbox/changes-mesos-framework