No sync, but use a ConcurrentHashMap.

git-svn-id: https://svn.apache.org/repos/asf/tomee/tomee/branches/tomee-1.7.x@1612313 13f79535-47bb-0310-9956-ffa450edef68
Revert experiment.

git-svn-id: https://svn.apache.org/repos/asf/tomee/tomee/branches/tomee-1.7.x@1612317 13f79535-47bb-0310-9956-ffa450edef68