update x/net/http2 to address few bugs (#11144)

additionally also configure http2 healthcheck
values to quickly detect unstable connections
and let them timeout.

also use single transport for proxying requests

cmd/globals.go

@@ -171,7 +171,7 @@ var (
 	globalRootCAs *x509.CertPool
 
 	// IsSSL indicates if the server is configured with SSL.
-	globalIsSSL bool
+	globalIsTLS bool
 
 	globalTLSCerts *certs.Manager
 
@@ -280,6 +280,8 @@ var (
 
 	globalInternodeTransport http.RoundTripper
 
+	globalProxyTransport http.RoundTripper
+
 	globalDNSCache *xhttp.DNSCache
 	// Add new variable global values here.
 )