Add failure filter to session.auth(...) deferred

Application errors where being reported as authentication errors.
Add failure filter to then(...) to handle authentication errors
and allow the otherwise(...) statement to handle application
errors.

Change-Id: Ib61fe22838959d970925cb09ed133bf60dee7a3b
Merge topic 'vtkweb-improve-auth-errors' into master

4b03a9b9 Add failure filter to session.auth(...) deferred