ZooZap should deal with /tracers being missing

2016-03-14 16:57:15,316 [util.ZooZap] ERROR: Exception running zapDirectory.
org.apache.zookeeper.KeeperException$NoNodeException: KeeperErrorCode = NoNode for /tracers
	at org.apache.zookeeper.KeeperException.create(KeeperException.java:111)
	at org.apache.zookeeper.KeeperException.create(KeeperException.java:51)
	at org.apache.zookeeper.ZooKeeper.getChildren(ZooKeeper.java:1532)
	at org.apache.zookeeper.ZooKeeper.getChildren(ZooKeeper.java:1560)
	at org.apache.accumulo.fate.zookeeper.ZooReader.getChildren(ZooReader.java:151)
	at org.apache.accumulo.server.util.ZooZap.zapDirectory(ZooZap.java:117)
	at org.apache.accumulo.server.util.ZooZap.main(ZooZap.java:110)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:606)
	at org.apache.accumulo.start.Main$2.run(Main.java:130)
	at java.lang.Thread.run(Thread.java:745)