Upgrade ONOS to karaf version 4.2.6

Change-Id: I9d4086378ee42c65e8865bd1172107767bdc028d
diff --git a/tools/build/build-offline-karaf b/tools/build/build-offline-karaf
index fdcdbdd..128db1c 100755
--- a/tools/build/build-offline-karaf
+++ b/tools/build/build-offline-karaf
@@ -1,7 +1,7 @@
 #!/bin/bash
  
-KARAF_RELEASE_VERSION="4.2.5"
-KARAF_BASE_PACKAGE_VERSION="4.2.5"
+KARAF_RELEASE_VERSION="4.2.6"
+KARAF_BASE_PACKAGE_VERSION="4.2.6"
 KARAF_TARFILE_NAME="apache-karaf-${KARAF_RELEASE_VERSION}.tar"
 ADDED_BOOT_FEATURES="kar/${KARAF_RELEASE_VERSION},webconsole/${KARAF_RELEASE_VERSION},scr/${KARAF_RELEASE_VERSION},war/${KARAF_RELEASE_VERSION}"