[metrics] Modify metrics 'raft_term' and 'time_since_last_leader_heartbeat' to MAX merge type
[metrics] Modify metrics 'raft_term' and 'time_since_last_leader_heartbeat' to MAX merge type

Change-Id: I915e4a4121175ff58bd814090f67fe99edef7141
Reviewed-on: http://gerrit.cloudera.org:8080/14933
Tested-by: Kudu Jenkins
Reviewed-by: Adar Dembo <866ca730bfc7f544e3ebce604ceeba4879f23df0@cloudera.com>
Reviewed-by: Alexey Serbin <864f6b82bd94e8dda64141d4274519ee66e0102e@cloudera.com>

helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu