Probe revamped to provide for a new WrappedError struct to wrap probes as error interface

This convenience was necessary to be used for golang library functions like io.Copy and io.Pipe
where we shouldn't be writing proxies and alternatives returning *probe.Error

This change also brings more changes across code base for clear separation regarding where an error
interface should be passed encapsulating *probe.Error and where it should be used as is.

pkg/controller/rpc.go

@@ -40,11 +40,11 @@ type RPCRequest struct {
 func NewRequest(url string, op RPCOps, transport http.RoundTripper) (*RPCRequest, *probe.Error) {
 	params, err := json.EncodeClientRequest(op.Method, op.Request)
 	if err != nil {
-		return nil, probe.New(err)
+		return nil, probe.NewError(err)
 	}
 	req, err := http.NewRequest("POST", url, bytes.NewReader(params))
 	if err != nil {
-		return nil, probe.New(err)
+		return nil, probe.NewError(err)
 	}
 	rpcReq := &RPCRequest{}
 	rpcReq.req = req
@@ -60,7 +60,10 @@ func NewRequest(url string, op RPCOps, transport http.RoundTripper) (*RPCRequest
 func (r RPCRequest) Do() (*http.Response, *probe.Error) {
 	resp, err := r.transport.RoundTrip(r.req)
 	if err != nil {
-		return nil, probe.New(err)
+		if werr, ok := probe.ToWrappedError(err); ok {
+			return nil, werr.ToError().Trace()
+		}
+		return nil, probe.NewError(err)
 	}
 	return resp, nil
 }