Upgrade ONOS to karaf version 4.2.6

Change-Id: I9d4086378ee42c65e8865bd1172107767bdc028d
diff --git a/tools/build/envDefaults b/tools/build/envDefaults
index 8eaecba..54779ae 100644
--- a/tools/build/envDefaults
+++ b/tools/build/envDefaults
@@ -5,7 +5,7 @@
 
 # M2 repository and Karaf gold bits
 export M2_REPO=${M2_REPO:-~/.m2/repository}
-export KARAF_VERSION=4.2.5
+export KARAF_VERSION=4.2.6
 export KARAF_ZIP=${KARAF_ZIP:-~/Downloads/apache-karaf-$KARAF_VERSION.zip}
 export KARAF_TAR=${KARAF_TAR:-~/Downloads/apache-karaf-$KARAF_VERSION.tar.gz}
 export KARAF_DIST=$(basename $KARAF_ZIP .zip)