FELIX-4000 avoid possibility of concurrentModificationException on m_dependencyManagers by never changing it

git-svn-id: https://svn.apache.org/repos/asf/felix/trunk@1462798 13f79535-47bb-0310-9956-ffa450edef68
FELIX-4004 Make DependencyManager.MultipleStaticCustomizer thread safe

git-svn-id: https://svn.apache.org/repos/asf/felix/trunk@1462799 13f79535-47bb-0310-9956-ffa450edef68