do not include tags and selectors in on-the-wire protocol

The new tag and selector fields must not be included in the msgpack
messages sent towards the backend, as they will not be expected by the
receiving side.

Author: satta

observation/input_observation.go

@@ -18,8 +18,8 @@ type InputObservation struct {
 	SensorID       string                   `codec:"I"`
 	TimestampEnd   time.Time                `codec:"L"`
 	TimestampStart time.Time                `codec:"F"`
-	Tags           map[string]struct{}      `codec:"G,omitempty"`
-	Selectors      map[interface{}]struct{} `codec:"S,omitempty"`
+	Tags           map[string]struct{}      `codec:"-,omitempty"`
+	Selectors      map[interface{}]struct{} `codec:"-,omitempty"`
 }
 
 // InChan is the global input channel delivering InputObservations from