fixes currator healthcheck

Previous check would always fail when a namespace was provided:

! zookeeper-curator-localhost:2181-data-state: ERROR
!  Path must not end with / character

java.lang.IllegalArgumentException: Path must not end with / character
	at org.apache.zookeeper.common.PathUtils.validatePath(PathUtils.java:58)
	at org.apache.zookeeper.ZooKeeper.exists(ZooKeeper.java:1020)
	at com.netflix.curator.framework.imps.ExistsBuilderImpl$2.call(ExistsBuilderImpl.java:171)
	at com.netflix.curator.framework.imps.ExistsBuilderImpl$2.call(ExistsBuilderImpl.java:160)
	at com.netflix.curator.RetryLoop.callWithRetry(RetryLoop.java:106)
	at com.netflix.curator.framework.imps.ExistsBuilderImpl.pathInForeground(ExistsBuilderImpl.java:156)
	at com.netflix.curator.framework.imps.ExistsBuilderImpl.forPath(ExistsBuilderImpl.java:147)
	at com.netflix.curator.framework.imps.ExistsBuilderImpl.forPath(ExistsBuilderImpl.java:35)
	at com.datasift.dropwizard.curator.health.CuratorHealthCheck.check(CuratorHealthCheck.java:39)
	at com.yammer.metrics.core.HealthCheck.execute(HealthCheck.java:195)