Always run the frame sizing code when a menubar is set

This is needed to properly set the size of a new menubar which is replacing one
with the same height, while also allowing the fixes from r67149 and r66344 to work.


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@73364 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775