Remove OperationContext.readModelForUpdate() or fix impl to not create resources

OperationContextImpl.readModelForUpdate() creates the target resource if it is not found. That's not good; createResource or addResource are for that and readResourceForUpdate does not do this.

No code in WF itself actually calls this method.

Either:

1) Remove the method (it's been deprecated since June 2011)
2) Change the impl to a simple readResourceForUpdate(address).getModel()