server: Use default logging configuration instead of zap production one

This fixes problem where logs json changes format of timestamp.

pkg/proxy/server.go

@@ -37,17 +37,8 @@ var (
 	defaultDialTimeout   = 3 * time.Second
 	defaultBufferSize    = 48 * 1024
 	defaultRetryInterval = 10 * time.Millisecond
-	defaultLogger        *zap.Logger
 )
 
-func init() {
-	var err error
-	defaultLogger, err = zap.NewProduction()
-	if err != nil {
-		panic(err)
-	}
-}
-
 // Server defines proxy server layer that simulates common network faults:
 // latency spikes and packet drop or corruption. The proxy overhead is very
 // small overhead (<500μs per request). Please run tests to compute actual
@@ -240,9 +231,6 @@ func NewServer(cfg ServerConfig) Server {
 	if s.retryInterval == 0 {
 		s.retryInterval = defaultRetryInterval
 	}
-	if s.lg == nil {
-		s.lg = defaultLogger
-	}
 
 	close(s.pauseAcceptc)
 	close(s.pauseTxc)