We've been getting failures lately on the first page load, I
think because Firefox is getting even more grindy on startup. So
turn the 'sleep' into a 'wait_still_screen', extend another wait,
and tweak the 'browser' needle so it only matches after the
bookmark bar has loaded rather than as soon as half the chrome
appears. Also make all the wait_still_screens use similarity 45
for consistency (flashing cursor could be there on any of them).
Signed-off-by: Adam Williamson <awilliam@redhat.com>
