Clear spwaned instances during tests

Fix tests on rackspace

Change-Id: I3aa29a3c68994145bc4ca4b8fc9437c3e574e5d7
Merge commit 'refs/changes/83/783/1' of ssh://gerrit.tuleap.net:29418/tuleap into tuleap-stable-master

* ssh://gerrit.tuleap.net:29418/tuleap:
  Clear spwaned instances during tests

Change-Id: I4677627dfc6ed4a5726b142cef40c031d8831b77