Reduce selenium server start timeout

This allows up to 4 restart attempts per regular 120000 test startup
timeout, instead of the previous 1-ish.
Merge branch 'master' into test-consistency
Upgrade selenium-webdriver to 2.44.0
Mock-authenticate while on static URL

To mock-authenticate, we have to get a URL on the site first so that we
can set a domain cookie via ``executeScript``.  We were using the site's
homepage for that, but it's slow, especially with the large Vimeo video
and google spreadsheet now getting pulled down on each pageload.
Instead, always grab the lightest (static) page we have on the site to
do authenticating.

Also increase the selenium startup timeout to 24000 ms (4 minutes) so
that we can have 4 attempts to start the selenium server with
~60000 ms timeouts each before we time out.  Travis is sometimes flakey
about starting selenium.
Use the same browser through session joining tests
Multiple fixes for test consistency

 - Rewrite ``framedDisconnectionModalShowing`` in
   ``test.session-joining.selenium.js`` to correct its logic. Instead of
   merely checking that the modal's dom element exists, check that it
   exists and is currently showing.  The old logic was incorrect, and
   only passed if the test runner inquired about the dom element during
   an unfinished page load, something that happened more consistently on
   faster machines, and less consistently on constrained environments
   like travis-ci.  This is perhaps the biggest contributor to test
   inconsistency this test suite has had to date.

 - Instead of throwing an alert on "hideApp" in mock-unhangout, just
   log, so that selenium drivers don't have to contend with clearing an
   alert if they take longer than 15 seconds to load.

 - Pass if video embeds in create-hoa to return as either "http:" or
   "https:"; we can't predict which the youtube CDN's will deliver.

 - Tolerate redraws of sessions in the moments before attempting to
   delete them in ``test.session-joining.selenium.js``
Merge pull request #375 from drewww/test-consistency

Test consistency