Service of disabled plugin should not be activated

Fix request #4617: Plugin service is enabled whereas the plugin is
disabled for the platform

Change-Id: Ie52f76f087e41545a62fb36b17b1d395facdcc8b
Merge commit 'refs/changes/61/2361/2' of ssh://gerrit.tuleap.net:29418/tuleap into tuleap-stable-master

* ssh://gerrit.tuleap.net:29418/tuleap:
  Service of disabled plugin should not be activated

Conflicts:
	src/common/autoload.php

Change-Id: Idcfbced2d6ef0de40418fd9271327e3603c83f3b
Tuleap 6.12.99.97

Change-Id: I5469da5965499cecd7ac972520b25583e432bccd