Fix possible intermittent test failures in the login test.
Fix possible intermittent test failures in the login test.

A couple other things seem to still be contributing to intermittent test
failures here. But by splitting these up into separate tests (rather
than having multiple "visit" calls inside one test) and clearing the
memroy cache between tests, that seems to fix the odd issues with
Poltergeist. This now seems to run smoothly after lots of repeated runs
(fingers crossed).

apinf/api-umbrella,apinf/api-umbrella,NREL/api-umbrella,NREL/api-umbrella,apinf/api-umbrella,apinf/api-umbrella,NREL/api-umbrella,apinf/api-umbrella,NREL/api-umbrella