Bracket normalization in BP_Activity_Activity::append_comments()

git-svn-id: https://buddypress.svn.wordpress.org/trunk@8003 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Clear activity item cache when it receives comments

r7997 fixed a bug was causing single activity items not to be cached properly
when a BP_Activity_Activity object was instantiated. This fix uncovered a bug
in activity commenting, where the activity parent was cached as childless, and
the cache was not invalidated when a new comment was posted.

See #5434

git-svn-id: https://buddypress.svn.wordpress.org/trunk@8004 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Normalize the cache keys and group name used for activity comments

wp_cache_get( $aid, 'bp_activity_comments' )

is more in line with single item caching across other components.

See r7956, r7997

See #5434

git-svn-id: https://buddypress.svn.wordpress.org/trunk@8005 cdf35c40-ae34-48e0-9cc9-0c9da1808c22