Potential fix fo background ping #54

When a node returns an error in ReqResp _before_ actually pulling the
response off the wire, close the tcp connection so that subsequent
requests dont try pulling the earlier response. Additionally, this
requires a change to try to re-dialing in the begining of ReqResp if
the node is not already connected.

Ran the tests locally and they passed, though obviously this situation is hard to repo.
cc @mrb @boj