ethereum/ratelimit: Fix bug in for timezones behind UTC

[albrow]

The following error was occurring at certain times of day for timezones that are behind UTC:

{
  "error_string": "rate: Wait(n=1) would exceed context deadline",
  "level": "error",
  "msg": "core app exited with error",
  "myPeerID": "16Uiu2HAkws8tB3zR8m7PQuV5iDNDfYXfShnWBLUeVpdefuTs8mqh",
  "time": "2019-11-06T17:38:55-08:00"
}

To be more specific, the bug seems to occur whenever the current local time is before midnight, but the time in UTC is the next day after midnight. When Mesh enters this state, no Ethereum RPC requests are allowed and Mesh cannot really function effectively.

[albrow]

@fabioberger I can manually confirm this fixes the bug, but ideally we should write a regression test to prevent this from popping up again. I can't figure out how to do that, and the existing tests always pass in my local timezone, regardless of time of day. Any ideas?