Group activity items not showing comment button for group members

[Venutius]

In the group activity page existing activity items are not displaying the comment icon for standard group members whilst it's displayed for site admin.

​https://buddypress.org/support/topic/comment-button-and-reply-not-showing/

[r-a-y]

Confirmed. This isn't specific to Nouveau. This is due to a typo by me to address #4429 :(

01.patch should fix this. Includes a unit test.

[DJPaul]

Milestone renamed

[r-a-y]

In 12131:

Groups: Fix display of "Comment" button in the activity stream.

In r11959, the banned group members check is using the wrong conditional.
This caused legitimate group members to never see the "Comment" button in
the activity stream.

This commit reverses the check and adds some unit tests (which should have
been written beforehand!).

Anti-props r-a-y.

See #4429.

Fixes #7854 (3.x branch).

[r-a-y]

In 12132:

Groups: Fix display of "Comment" button in the activity stream.

In r11959, the banned group members check is using the wrong conditional.
This caused legitimate group members to never see the "Comment" button in
the activity stream.

This commit reverses the check and adds some unit tests (which should have
been written beforehand!).

Anti-props r-a-y.

Fixes #7854 (trunk).