[LMS-1257] improved FailureExpectation command and simplified AuthenticationTest

.../client/web/client/application/AbstractAsyncCallback.java

...ric/client/web/client/application/AuthenticationTest.java

...enbis/generic/client/web/client/application/ui/Login.java

...nbis/generic/client/web/client/application/ui/Logout.java

.../web/client/testframework/AbstractDefaultTestCommand.java

...c/client/web/client/testframework/FailureExpectation.java

...generic/client/web/client/testframework/ITestCommand.java

...eneric/client/web/client/testframework/RemoteConsole.java

...client/testframework/WaitForAllActiveCallbacksFinish.java

...n/experiment/GenericExperimentAttachmentDownloadTest.java