Be explicit about activity dates in test_bp_has_activities_favorites_action_filter()

This ensures that we can predict the order in which they'll be returned from
bp_has_activities(), which will ensure that the tests pass on slower servers
where the create() methods are run in different seconds (like travis)

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7107 cdf35c40-ae34-48e0-9cc9-0c9da1808c22