Remove LatencyAccept of the reverse proxy from the e2e test

Part of the patches to fix #17737

During the development of #17938,
we agreed that during the transition to L7 forward proxy, unused
features and features targeting L4 reverse proxy will be dropped.

This feature falls under the unused feature. Also, the initial
implementation has a bug: if connections are not created continuously,
the latency accept will not work. Consider the following case:
a) set latency accept
b) put latency accept into effect
c) latency accept will start idling the goroutine
d) block-wait at accept() - waiting for new connections
e) new connection comes in - establish it
f) go to c -> as we can see, if the request come every x seconds, where
x is larger than the latency accept time we set, we can see that the
latency accept has no effect.

Signed-off-by: Chun-Hung Tseng <henrybear327@gmail.com>

Author: henrybear327

pkg/proxy/server.go

@@ -59,8 +59,6 @@ type Server interface {
 	// Close closes listener and transport.
 	Close() error
 
-	LatencyAccept() time.Duration
-
 	// DelayTx adds latency ± random variable for "outgoing" traffic
 	// in "sending" layer.
 	DelayTx(latency, rv time.Duration)
@@ -142,9 +140,6 @@ type server struct {
 	listenerMu sync.RWMutex
 	listener   net.Listener
 
-	latencyAcceptMu sync.RWMutex
-	latencyAccept   time.Duration
-
 	modifyTxMu sync.RWMutex
 	modifyTx   func(data []byte) []byte
 
@@ -263,17 +258,6 @@ func (s *server) listenAndServe() {
 	close(s.readyc)
 
 	for {
-		s.latencyAcceptMu.RLock()
-		lat := s.latencyAccept
-		s.latencyAcceptMu.RUnlock()
-		if lat > 0 {
-			select {
-			case <-time.After(lat):
-			case <-s.donec:
-				return
-			}
-		}
-
 		s.listenerMu.RLock()
 		ln := s.listener
 		s.listenerMu.RUnlock()
@@ -609,13 +593,6 @@ func (s *server) Close() (err error) {
 	return err
 }
 
-func (s *server) LatencyAccept() time.Duration {
-	s.latencyAcceptMu.RLock()
-	d := s.latencyAccept
-	s.latencyAcceptMu.RUnlock()
-	return d
-}
-
 func (s *server) DelayTx(latency, rv time.Duration) {
 	if latency <= 0 {
 		return