39 cooperative cancel

[LayneHaber]

The Problem

Fixes this in the client/node

The Solution

Call resolveCondition with a payment id and no secret to cancel a payment.

Checklist:

• I am making this PR against staging, not master
• My code follows the code style of this project.
• I have described any backwards-incompatibility implications above.
• I have highlighted which parts of the code should be reviewed most carefully.
• If my change requires a change to the documentation, I have updated it accordingly.