[sailfish-browser] Fix page loading on the TabPage

In case active tab is closed from the TabPage and you have
multiple tabs, the next available tab is activated and loaded.
In above case, we need to be able to resetHeight for the page.

Normally, height is reset when loading starts and
when loading ends. When container is invisible
we should not go to the "boundHeightControl" state as it
blocks resetHeight.
Merge pull request #105 from rainemak/fixLoadingFromTabPage

[sailfish-browser] Fix page loading on the TabPage