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/test/bin/onos-check-bits b/tools/test/bin/onos-check-bits
index be1b8da..6ce3ec9 100755
--- a/tools/test/bin/onos-check-bits
+++ b/tools/test/bin/onos-check-bits
@@ -32,7 +32,7 @@
   echo "ONOS archive does not contain the proper version file" && exit 1
 fi
 
-tar tzf ${ONOS_TAR} | grep -q apache-karaf-4.2.6
+tar tzf ${ONOS_TAR} | grep -q apache-karaf-4.2.8
 if [ $? -ne 0 ]; then
   echo "ONOS archive does not contain karaf" && exit 1
 fi