Upgrade to Apache Karaf 4.2.8 to support Kafka log appender

This is required for CORD. Karaf 4.2.6 explicitelly prevents loading of
some of the bundles required to support shipping logs via Karaf.

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