Fix PersistentTtlNode not deleted if touch node is never created

[chevaris]

This closes #1258 .

Thanks to Kezhu Wang for the suggestion in the solution

[kezhuw]

@chevaris Thank you for your contribution!

I left some inline comments.

[kezhuw]

Refs: CURATOR-545, ZOOKEEPER-3546(apache/zookeeper#1138), #1258

[kezhuw]

Thank you for your contribution!

Looks good in general. I left a comment about the way to inject code for testing purpose.

[kezhuw]

Would you want to take another look ? @tisonkun @eolivelli @Randgalt

It has been raised before in CURATOR-545, but end up in a fix in zookeeper side ZOOKEEPER-3546.

Given the fact that PERSISTENT_WITH_TTL is capable as CONTAINER node(see also
apache/zookeeper#1138 (comment)). I think we could create the container node with using PERSISTENT_WITH_TTL so we can fix this without reconfig server cluster.

Ideally, there sould be a "touch" command to modify "mtime" of PERSISTENT_WITH_TTL. Sadly, we don't have, so the child touch node still sound good to me as it does not setData on container node after creation.

[tisonkun]

LGTM. Thanks for your contribution @chevaris!