test: Wait for stream server checks to complete

The main test goroutine might be completed before checks on the server
goroutine are completed, hence cause the below panic issue. This commit
is to defer the streamDone channel close to make sure the error check on
the stream server is done before returning from the test. We keep the
time check on the wait in the end of each test to not stall the tests in
case the stream server fails to exit.

Panic error
```
panic: Fail in goroutine after Test/ServerSuite/TestRequestStaleNonce has completed
```

Testing was done as per below:
```
$ go test -count 500 -run Test/ServerSuite/TestRequestStaleNonce ./pkg/envoy/xds/...
ok      github.com/cilium/cilium/pkg/envoy/xds  250.866s
```

Fixes: cilium#31855
Signed-off-by: Tam Mach <tam.mach@cilium.io>
Signed-off-by: Jarno Rajahalme <jarno@isovalent.com>

Author: jrajahalme

pkg/envoy/xds/server_e2e_test.go

@@ -151,8 +151,8 @@ func (s *ServerSuite) TestRequestAllResources(c *C) {
 
 	// Run the server's stream handler concurrently.
 	go func() {
+		defer close(streamDone)
 		err := server.HandleRequestStream(ctx, stream, AnyTypeURL)
-		close(streamDone)
 		c.Check(err, IsNil)
 	}()
 
@@ -276,8 +276,8 @@ func (s *ServerSuite) TestAck(c *C) {
 
 	// Run the server's stream handler concurrently.
 	go func() {
+		defer close(streamDone)
 		err := server.HandleRequestStream(ctx, stream, AnyTypeURL)
-		close(streamDone)
 		c.Check(err, IsNil)
 	}()
 
@@ -401,8 +401,8 @@ func (s *ServerSuite) TestRequestSomeResources(c *C) {
 
 	// Run the server's stream handler concurrently.
 	go func() {
+		defer close(streamDone)
 		err := server.HandleRequestStream(ctx, stream, AnyTypeURL)
-		close(streamDone)
 		c.Check(err, IsNil)
 	}()
 
@@ -574,8 +574,8 @@ func (s *ServerSuite) TestUpdateRequestResources(c *C) {
 
 	// Run the server's stream handler concurrently.
 	go func() {
+		defer close(streamDone)
 		err := server.HandleRequestStream(ctx, stream, AnyTypeURL)
-		close(streamDone)
 		c.Check(err, IsNil)
 	}()
 
@@ -676,8 +676,8 @@ func (s *ServerSuite) TestRequestStaleNonce(c *C) {
 
 	// Run the server's stream handler concurrently.
 	go func() {
+		defer close(streamDone)
 		err := server.HandleRequestStream(ctx, stream, AnyTypeURL)
-		close(streamDone)
 		c.Check(err, IsNil)
 	}()
 
@@ -815,8 +815,8 @@ func (s *ServerSuite) TestNAck(c *C) {
 
 	// Run the server's stream handler concurrently.
 	go func() {
+		defer close(streamDone)
 		err := server.HandleRequestStream(ctx, stream, AnyTypeURL)
-		close(streamDone)
 		c.Check(err, IsNil)
 	}()
 
@@ -949,8 +949,8 @@ func (s *ServerSuite) TestNAckFromTheStart(c *C) {
 
 	// Run the server's stream handler concurrently.
 	go func() {
+		defer close(streamDone)
 		err := server.HandleRequestStream(ctx, stream, AnyTypeURL)
-		close(streamDone)
 		c.Check(err, IsNil)
 	}()
 
@@ -1082,8 +1082,8 @@ func (s *ServerSuite) TestRequestHighVersionFromTheStart(c *C) {
 
 	// Run the server's stream handler concurrently.
 	go func() {
+		defer close(streamDone)
 		err := server.HandleRequestStream(ctx, stream, AnyTypeURL)
-		close(streamDone)
 		c.Check(err, IsNil)
 	}()