Bug: Fix stupid edit section cta bug

Steps to reproduce:
* Set hash to #section_2 and load page whilst logged in
* Click edit button
* Close overlay
* Scroll to top and view rendering mess.

It seems setting height on the body tag is the cause.
Since we only use this for small pages only set it when navigation-enabled
class is on.

Change-Id: I76e81d2bfed291c307759e91ae9912ce58edacf6