MINOR: stats: remove the autofocus on the scope input field

MINOR: stats: remove the autofocus on the scope input field

commit 88c278fadf provided a new input field on the statistics page which was
focused by default. The autofocus prevent to scroll down the page with the
keyboard immediately afterloading it, without the need to leave that field.
It also interfered with "stats refresh" by scrolling up to this field on each
refresh.

This small patch removes the autofocus keyword and adds a tabindex="1" as
suggested by Vincent Bernat. It also cleans up the generated html code.