FELIX-3956 - JAAS Support bundle should have optional dependency on Servlet API

Marking the javax.servlet package as optional. And handling exception while creating plugin instance in absence of servlet api

git-svn-id: https://svn.apache.org/repos/asf/felix/trunk@1453296 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/jaas/pom.xml b/jaas/pom.xml
index 8e5072e..167b41e 100644
--- a/jaas/pom.xml
+++ b/jaas/pom.xml
@@ -87,6 +87,10 @@
                         <Bundle-Activator>
                             org.apache.felix.jaas.internal.Activator
                         </Bundle-Activator>
+                        <Import-Package>
+                          javax.servlet.*;resolution:=optional,
+                          *
+                        </Import-Package>
                         <_removeheaders>
                             Embed-Dependency,Private-Package,Include-Resource
                         </_removeheaders>