Fix build issue in modeshape-web-jcr-rest-client that may randomly occur

Seeing the following failures when the junit tests are run for modeshape-web-jcr-rest-client:

Failed tests:
shouldPublishDdlResource(org.modeshape.web.jcr.rest.client.json.JsonRestClientTest):
shouldPublishNonVersionableResourceMultipleTimes(org.modeshape.web.jcr.rest.client.json.JsonRestClientTest):
shouldPublishMVersionableResourceMultipleTimes(org.modeshape.web.jcr.rest.client.json.JsonRestClientTest):