Fix race condition when setting the request state to active

Call SetState(State_Active) before signalling the worker thread, as
otherwise it would be possible for it to wake up and set its state to
something else before it was reset to "active" from the main thread.

This fixed another TSAN error.

src/common/webrequest_curl.cpp

@@ -230,16 +230,13 @@ bool wxWebRequestCURL::StartRequest()
 {
     m_bytesSent = 0;
 
-    if ( m_sessionImpl.StartRequest(*this) )
-    {
-        SetState(wxWebRequest::State_Active);
-        return true;
-    }
-    else
+    if ( !m_sessionImpl.StartRequest(*this) )
     {
         SetState(wxWebRequest::State_Failed);
         return false;
     }
+
+    return true;
 }
 
 void wxWebRequestCURL::Cancel()
@@ -517,6 +514,8 @@ bool wxWebSessionCURL::StartRequest(wxWebRequestCURL & request)
             return false;
     }
 
+    request.SetState(wxWebRequest::State_Active);
+
     // Signal the worker thread to resume work
     wxMutexLocker lock(m_mutex);
     m_condition.Signal();