Upgrade to Apache Karaf 4.2.8

Change-Id: I8ae525e6c8a04c0381c5e3bac39de1a7b85b4446
diff --git a/tools/package/onos_stage.py b/tools/package/onos_stage.py
index 466c016..e11a3fa 100755
--- a/tools/package/onos_stage.py
+++ b/tools/package/onos_stage.py
@@ -27,7 +27,7 @@
 
 written_files = set()
 now = time.time()
-karaf_version = "4.2.6"
+karaf_version = "4.2.8"
 karaf_system = "apache-karaf-" + karaf_version + "/system/"
 
 def addFile(tar, dest, file, file_size):