Adjust acceptance tests to the new share link UI

The share link UI no longer uses its own layout below the other shares;
now it is shown as a share row with a menu for the actions (except
enabling it, which is shown in the row itself), just like the other
shares.

The share link is no longer shown, either; now the link is got by
clicking on a "Copy URL" menu item, which copies the link to the
clipboard. As the clipboard is not accessible from the acceptance tests
the URL is now extracted from the attributes of that menu item (although
the menu item is clicked anyway to mimic the user behaviour).

Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>