Remove usage of ocstatus package

This changes the tracing package to accept an error on SetStatus, which
is really what we always want anyway.
This also decouples the trace package from opencensus.

trace/opencensus/opencensus.go

@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"sync"
 
+	"github.com/virtual-kubelet/virtual-kubelet/errdefs"
 	"github.com/virtual-kubelet/virtual-kubelet/log"
 	"github.com/virtual-kubelet/virtual-kubelet/trace"
 	octrace "go.opencensus.io/trace"
@@ -46,7 +47,30 @@ func (s *span) End() {
 	s.s.End()
 }
 
-func (s *span) SetStatus(status trace.Status) {
+func (s *span) SetStatus(err error) {
+	if !s.s.IsRecordingEvents() {
+		return
+	}
+
+	var status octrace.Status
+
+	if err == nil {
+		status.Code = octrace.StatusCodeOK
+		s.s.SetStatus(status)
+		return
+	}
+
+	switch {
+	case errdefs.IsNotFound(err):
+		status.Code = octrace.StatusCodeNotFound
+	case errdefs.IsInvalidInput(err):
+		status.Code = octrace.StatusCodeInvalidArgument
+		// TODO: other error types
+	default:
+		status.Code = octrace.StatusCodeUnknown
+	}
+
+	status.Message = err.Error()
 	s.s.SetStatus(status)
 }