Adds unit tests for bp_group_has_members()

These will help ensure that any refactoring associated with #4482 will not
break backward compatibility.

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7090 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Don't use extract in bp_group_has_members. See #4482

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7091 cdf35c40-ae34-48e0-9cc9-0c9da1808c22