Created Unassigned: http_listener blocks on single core machine [106]

The http_listener class blocks on Windows if the machine has a single core (e.g. small Azure VMs)

Following code for repro (and workaround)

#include "stdafx.h"
#include <cpprest/http_listener.h>
#include <cpprest/filestream.h>

using namespace web::http::experimental::listener;
using namespace web::http;
using namespace web;

// Set this to 1 to show the fix
// Setting 0 will cause hang on single core machines (like small Azure instances)
#define SET_MIN_CONCURRENCY 0

int _tmain(int argc, _TCHAR* argv[])
{
#if SET_MIN_CONCURRENCY
// This policy fixes the issue
concurrency::CurrentScheduler::Create(Concurrency::SchedulerPolicy(1, 2, Concurrency::MinConcurrency));
// oversubscribe isn't sufficient
//concurrency::Context::Oversubscribe(true);
#endif

http_listener listener(U("http://+:80/test"));

listener.support(methods::GET, [&](http_request request)
{
request.reply(status_codes::OK, U("Hello, world"));
});

puts("Opening http://localhost/test for serving");

listener.open().wait();

puts("Press [enter] to quit");

std::string line;
std::getline(std::cin, line);

listener.close().wait();

#if SET_MIN_CONCURRENCY
//concurrency::Context::Oversubscribe(false);

concurrency::CurrentScheduler::Detach();
#endif

return 0;
}