Servlet should have had serial version.

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1450033 13f79535-47bb-0310-9956-ffa450edef68
SLING-2755 Fixed.

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1450034 13f79535-47bb-0310-9956-ffa450edef68