allowing better check on conversation if it is busy or not - main issue is we dont control cause of our spi where a boolean is set (servlet layer? jsf layer?...) so we need to support multiple calls by thread + avoid to serialize the conversation itself but use conversation manager for it

git-svn-id: https://svn.apache.org/repos/asf/openwebbeans/trunk@1648291 13f79535-47bb-0310-9956-ffa450edef68