Node contracts without any resources used

[AhmedHanafy725]

anyone can create a node contract but the contract may not be attached to a deployment and this contract will block the node from being rented as it has a contract. So anyone can create contracts on all nodes (this will cost him only the extrinsic fee) and break the feature of renting a free node without being in a dedicated farm.

Related Issues

• https://github.com/threefoldtech/tfgrid-sdk-go/issues/175

not sure what should be done in this case but as suggestions:

• the node contract should be paid a periodic fee even if it doesn't have a deployment.
• the node contract should have a lifetime. and if it doesn't have any resource report, it should be deleted.