tdf#122112 Hide the menu bar when the notebookbar is locked

Only reproducible with GTK3 (maybe KDE5?).
This way we ensure a uniformed behavior across vclplugins anyway

Change-Id: I6edd6a426cb206d797b504ddcdcef999f79fa3c8
Reviewed-on: https://gerrit.libreoffice.org/65189
Tested-by: Jenkins
Reviewed-by: Xisco FaulĂ­ <xiscofauli@libreoffice.org>
(cherry picked from commit 21b81b07b01e4482a80ced8dcdf48c480031c3c8)
Reviewed-on: https://gerrit.libreoffice.org/65197
diff --git a/sfx2/source/notebookbar/SfxNotebookBar.cxx b/sfx2/source/notebookbar/SfxNotebookBar.cxx
index 5dcaea7..1ff5a8c 100644
--- a/sfx2/source/notebookbar/SfxNotebookBar.cxx
+++ b/sfx2/source/notebookbar/SfxNotebookBar.cxx
@@ -188,11 +188,13 @@
void SfxNotebookBar::LockNotebookBar()
{
    m_bHide = true;
    m_bLock = true;
}

void SfxNotebookBar::UnlockNotebookBar()
{
    m_bHide = false;
    m_bLock = false;
}

bool SfxNotebookBar::IsActive()