Activity Integration don't call every activity plugins

Do not return every time, otherwise all triggers like onBeforePost will just work on the first plugin and not on the other.
This patch will not fix the compatibility with the existing plugins because some are returning "true" for generic triggers.
It is also possible to get all values and return a merge of these, but the __call function must call every activity plugins.
The "no return" was fine for me but I tried to manage the issue #2225
Which results the commit https://github.com/obsidev/Kunena-Forum/commit/9a08827ac588e244bddc82ee0396c9e8e470a159