Fix https://bz.apache.org/bugzilla/show_bug.cgi?id=60918

      When sendfile processing passes to the Poller for completion and then completes before Http11Processor.service() exists, the Processor is recycled which clears sendfileData causing the Processor to return CLOSED or OPEN rather than SENDFILE.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc8.5.x/trunk@1788546 13f79535-47bb-0310-9956-ffa450edef68