shell: Reset active view to allow further activation

shell: Reset active view to allow further activation

Going back to regular, with a none orientation would allow to re-activate the
window. This wouldn't happen because we haven't been able to reset
the active window

Keeps things sane for the user and would allow navigating back to
those windows. Further patches should improve and avoid this entirely if
the split window is sticky.

Bug-AGL: SPEC-4839
Signed-off-by: Marius Vlad <marius.vlad@collabora.com>
Change-Id: Ic2cc7fd2839f5a664957d3f111c400559d93cf3f