buddypress()->activity->actions in unit tests

[imath]

If you look at #6126, you'll see that i've discovered a trouble when directly using BP_Activity_Activity( $id ). I've found this bug lately because when running the complete tests suite, everything seemed to work fine. It's only when i've run only a couple of tests i've discovered this issue.

The problem was located in tests where i wasn't resetting the global buddypress()->activity->actions the right way. As a result the following tests were not only dealing with the default activity actions but also with post types activities actions.
I've also discovered some other troubles like the fact once a post type (for instance the 'page' one) were added to the post types to track, some bp_activity properties were still set for the following tests.

So i've edited each test and made sure the globals were properly reset -> see *.pertest.patch

But as boonebgorges suggested in this ​comment, i think we should use the BP_UnitTestCase->setUp() method to be sure for the future tests we'll build we won't have to think about how to completely reset globals a test about post types activities edited. This way each new test will always get a default buddypress()->activity->actions. -> see *.setUp.patch

What do you think ?

[imath]

Let's see this in 2.3

[imath]

In 10545:

Post Type Activities: add unit tests and improve existing ones.

See #6482
Fixes #6128