Upgrade to Apache Karaf 4.2.8

Change-Id: I8ae525e6c8a04c0381c5e3bac39de1a7b85b4446
diff --git a/tools/package/deb/prerm b/tools/package/deb/prerm
index ee32a56..7c7106e 100755
--- a/tools/package/deb/prerm
+++ b/tools/package/deb/prerm
@@ -14,7 +14,7 @@
 
 # Clean up onos runtime directories
 #      TODO don't hardcode karaf version
-rm -rf /opt/onos/apache-karaf-4.2.6/
+rm -rf /opt/onos/apache-karaf-4.2.8/
 rm -rf /opt/onos/var/*
 rm -rf /opt/onos/config
 rm -rf /opt/onos/options