Fix typo in bp_activity_add_meta() tests

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7874 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Introduce groups_add_groupmeta(). See #5400

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7875 cdf35c40-ae34-48e0-9cc9-0c9da1808c22