create persistent sequential node with empty bytes

[ssalinas]

@tpetr ObjectMapper will still throw an error if it's given empty bytes. So I modified the readFromZk method to check for data length as well as updating the persistent sequential to be created with empty bytes. If we get empty bytes we return an absent

Context for others:

• When curator creates a persistent sequential node with no argument for content/data, it defaults the data to the ip of the client creating it. It was possible that BaragonService would try to read this in between the creation of the node and setting the data in the addAgentResponse method in the BaragonAgentResponseDatastore

[tpetr]

LGTM

[tpetr]

I like that we're explicit with what data to set, but I also wonder if we should just override Curator's default value, so that we don't possibly get bitten by this in other places too?

[ssalinas]

@tpetr updated the defaultData to new byte[] {} in the BaragonServiceModule

[jhaber]

nit: new byte[0]?

[ssalinas]

updated 👍