Offset the taps on the browser toolbar buttons

@bobsilverberg, I don't want to get too excited too soon but I am pretty confident about this!

Offset the taps on the badge and on the url go button because sometimes the system update notification pops open right after the startup and it hijacks the tap.

The best solution is to get bug 876723 in. I'm now wondering if this is to blame for some other flaky tests too.

branches:
`v1.0.1` -> Tested OK
`v1-train` -> Tested OK
`desktop` -> Not affected but tested and safe to merge

http://qa-selenium.mv.mozilla.com:8080/job/b2g.unagi.gaia.v1-train.ui.run_adhoc_tests/43/console