SLING-2704 : NPE in JspScriptEngineFactory in case JSP bundle restart while servicing request. Applied patch from Chetan Mehrotra

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1436923 13f79535-47bb-0310-9956-ffa450edef68
Use snapshot version to include SLING-2704

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1436926 13f79535-47bb-0310-9956-ffa450edef68