Live: Crash for invalid live stream state when unmount HTTP. v6.0.146 v7.0.3 (#4141)

When unpublishing, the handler callback that will stop the coroutine:

```cpp
_can_publish = true;
handler->on_unpublish(req);
```

In this handler, the `http_unmount` will be called:

```cpp
void SrsHttpStreamServer::http_unmount(SrsRequest* r)
    cache->stop();
```

In this `http_unmount` function, there could be context switching. In
such a situation, a new connection might publish the stream while the
unpublish process is freeing the stream, leading to a crash.

To prevent a new publisher, we should change the state only after all
handlers and hooks are completed.

---------

Co-authored-by: liumengte <liumengte@visionular.com>
Co-authored-by: winlin <winlinvip@gmail.com>

trunk/src/app/srs_app_source.cpp

@@ -2632,8 +2632,7 @@ void SrsLiveSource::on_unpublish()
     meta->update_previous_ash();
 
     srs_trace("cleanup when unpublish");
-    
-    _can_publish = true;
+
     if (!_source_id.empty()) {
         _pre_source_id = _source_id;
     }
@@ -2655,6 +2654,8 @@ void SrsLiveSource::on_unpublish()
     if (consumers.empty()) {
         stream_die_at_ = srs_get_system_time();
     }
+
+    _can_publish = true;
 }
 
 srs_error_t SrsLiveSource::create_consumer(SrsLiveConsumer*& consumer)

trunk/src/core/srs_core_version6.hpp

@@ -9,6 +9,6 @@
 
 #define VERSION_MAJOR       6
 #define VERSION_MINOR       0
-#define VERSION_REVISION    145
+#define VERSION_REVISION    146
 
 #endif

trunk/src/core/srs_core_version7.hpp

@@ -9,6 +9,6 @@
 
 #define VERSION_MAJOR       7
 #define VERSION_MINOR       0
-#define VERSION_REVISION    2
+#define VERSION_REVISION    3
 
 #endif