Fix random failures when testing closing of the sidebar and restarting the browser

This adds in a bit of wait time, so that if the sidebar is slow in talking to the server to re-log in the test can still succeed.

I suggest r=@dmose or r=@tOkeshu for review.

It'd be nice to run travis several times to ensure it passes. I'll only let travis run as I push this PR. The reviewer can choose to either trigger more runs, or to get me to do that before merge.