logs: change timestamp to ISO (#1708)

Co-authored-by: Vishal <vishal-biyani@users.noreply.github.com>

cmd/fetcher/main.go

@@ -20,13 +20,16 @@ import (
 	"log"
 
 	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
 
 	"github.com/fission/fission/cmd/fetcher/app"
 )
 
 // Usage: fetcher <shared volume path>
 func main() {
-	logger, err := zap.NewProduction()
+	config := zap.NewProductionConfig()
+	config.EncoderConfig.EncodeTime = zapcore.ISO8601TimeEncoder
+	logger, err := config.Build()
 	if err != nil {
 		log.Fatalf("can't initialize zap logger: %v", err)
 	}