fn: default fnserver tag keys and api key adjustment (#1261)

Default fn server keys should be minimal (empty) since not
all stats have associated app name, fn id, etc.

API tags for requests should not include "status" as this is
part of responses.

cmd/fnserver/main.go

@@ -25,7 +25,7 @@ func main() {
 }
 
 func registerViews() {
-	keys := []string{"fn_appname", "fn_path"}
+	keys := []string{}
 
 	latencyDist := []float64{1, 10, 50, 100, 250, 500, 1000, 10000, 60000, 120000}
 
@@ -50,5 +50,5 @@ func registerViews() {
 	// Register s3 log views
 	s3.RegisterViews(keys, latencyDist)
 
-	server.RegisterAPIViews([]string{}, latencyDist)
+	server.RegisterAPIViews(keys, latencyDist)
 }