doc(deploying-apps.md): add note about known issue in controller (#395)
doc(deploying-apps.md): add note about known issue in controller (#395)

when deployments are turned on, the controller can crash on startup in
a very specific case

Ref https://github.com/deis/controller/issues/903

* doc(deploying-apps.md): add note about known issue

deis/workflow,deis/workflow,deis/workflow