Added support for setting a Synchronizer to BasicBuilderParameters.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1485393 13f79535-47bb-0310-9956-ffa450edef68
Reenabled a test case that was failing before.

The test method now sets a proper Synchronizer before accessing the test
configuration concurrently.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1485394 13f79535-47bb-0310-9956-ffa450edef68