Additional fix for BZ 56611
and remove method Tomcat$ExistingStandardWrapper.hasAsync(), because
1). This method should have been "final" as it is used by class constructor.
2). Wrapper.isAsyncSupported(), Wrapper.setAsyncSupported() are available as a replacement.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1604014 13f79535-47bb-0310-9956-ffa450edef68