Shut down the Timeline Service, switch to the newer version, and start the Timeline Service:
su - yarn -c "/usr/hdp/current/hadoop-yarn-timelineserver/sbin/yarn-daemon.sh
stop timelineserver"
hdp-select set hadoop-yarn-timelineserver 2.2.6.0-2800
su - yarn -c "/usr/hdp/current/hadoop-yarn-timelineserver/sbin/yarn-daemon.sh
start timelineserver"
