Detect nodes that variably limit their bandwidth

[MeijeSibbel]

Currently there are nodes that have monthly data bandwidth caps, they allow max Storj node throughput of data for the first few days and then when they are close to the limit they rate limit the Storj Share transfer speed. This will affect the renters, specially when they pay for a certain performance aspect as described in storj-archived/billing#71. These nodes should be detected and down-ranked. This would imply carrying out regular benchmarking tests through the month.

This is a potential problem in the bigger schemes of things, as farmers might once they fill all their drives completely limit (e.g. 1Kbs) upload traffic, this way they will still get paid for storage but the renter will never actually be able to retrieve the file. The Storj network should detect this, expire all the shards on that user's node, stop the payment and mirror the shards to another reliable node.

[braydonf]

Farmers holding data but aggressively limiting bandwidth is one reason why I think incentives for data transfer are most essential (in comparison with audits of storing data).

[braydonf]

IMO, this should be included in the exchange reports document #13