There should be a way for the scheduler to communicate to the client that the requested capabilities are not available

[e117649]

Currently there does not appear to be a way to do this, and the client just waits forever, while the scheduler keeps trying to get those capabilities.

[sharpener6]

@gxuu, can you implement this, it should return TaskResultFailed I think

[gxuu]

seems to be put on hold. revoke assignment from myself.