Hide the new progress bar in TvPlayWindow until it is used.

It is currently only updated for bluray startup. I'm investigating dvd
startup but it doesn't appear to be useful in the same way and most
normal playback startup is quick enough not to need it (for me at
least).

mythtv/libs/libmythtv/tv_play_win.cpp

@@ -35,6 +35,7 @@ bool TvPlayWindow::Create()
     m_progressBar = dynamic_cast<MythUIProgressBar*>(GetChild("progress"));
     if (m_progressBar)
     {
+        m_progressBar->SetVisible(false);
         m_progressBar->SetStart(0);
         m_progressBar->SetTotal(100);
         m_progressBar->SetUsed(m_progress);
@@ -51,6 +52,7 @@ void TvPlayWindow::UpdateProgress(void)
     if (m_progress > 100)
         m_progress = 0;
     m_progressBar->SetUsed(m_progress);
+    m_progressBar->SetVisible(true);
 }
 
 /** \brief Mouse click/movement handler, recieves mouse gesture events