API.login - don't show error modal on login error
API.login - don't show error modal on login error

because when trying to login, we already show a flash on failure

(depends on changes in fcc6248, #2075)

https://bugzilla.redhat.com/show_bug.cgi?id=1486616

ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic