Wait for login process to complete

IE sometimes will navigate to the next page before the login
process completes.  This causes bogus failures for example:

https://wmf.ci.cloudbees.com/job/UploadWizard-commons.wikimedia.beta.wmflabs.org-windows-internet_explorer_10/482/

Change-Id: I89638c67d9017dee158d958a6941d61e45499474