[Windows] Presence notification fill OS socket queue

[jstuczyn]

If you let your mixnode / provider running on Windows, eventually it will start failing to send presence with following errors:
2020-04-02T17:05:20.840 ERROR nym_sfw_provider::provider::presence > failed to send presence - Error(Hyper(Error(Connect, Os { code: 10055, kind: Other, message: "An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full." })), "http://localhost:8080/api/presence/mixproviders")

On top of that, establishing any other TCP connections on the host machine might fail until the mixnode process is killed.

A possible solution would be to perhaps introduce re-usable connections between nodes and the presence server.

[futurechimp]

Somebody is eventually going to join the testnet with a Windows machine. Should we make Windows mixnodes commit suicide until this problem is figured out? The last thing we want is packets going missing sporadically because someone is running an unsupported OS? I would put Windows in that category for the moment, I consider Linux to be our only real supported OS for running mixnodes at the moment.

[jstuczyn]

Seems to be related to seanmonstar/reqwest#284

[jstuczyn]

Also seems to be fixed in reqwest 0.10