[test][UsersView] Check existence of checkboxes for selecting delete items
[UsersView][HatoholMonitoringView] Fix visibility of delete button

The previous code has a bug that checkboxes for selecting delete
items aren't shown in spite of having a privilege.

github issue #686
[test][HatoholMonitoringView] Fix a broken test

The visibility of checkboxes for selecting delete items will be
managed by caller.