Fix for zookeeper backend

[chenchun]

Signed-off-by: Chun Chen ramichen@tencent.com

For both etcd and zookeeper, it's not allowed to watch a not exist node.
Tested on my laptop. Please don't review until docker/libkv#41 get's in.

[mavenugo]

@chenchun thanks for the fix. Can you pls take care of the circleci failure ?

[abronan]

@chenchun Sorry for the time spent reviewing your PR on libkv's side. Needs a rebase here :(

[chenchun]

@abronan thanks, I'll rebase after #466 getting merged cause this PR will introduce Godeps changes of libkv which conflicts with that in #466.

[mavenugo]

@chenchun now that we have the latest libkv, can u pls rebase ?

[chenchun]

@mavenugo , rebased.
Found a issue with CI. I actually rebased my PR yesterday, but I forgot to git fetch origin first. So my PR didn't include libkv updates and it failed. I am wondering is it expected that CI tests again PR branch instead of master branch with changes in PR?

[mrjana]

@chenchun CI cannot check against master since it may not be possible to merge without conflict all the time. So it always checks the PR version. That is why in a fast changing project like libnetwork it is always a good idea to rebase to the latest even if github didn't find any merge conflicts.

[chenchun]

@mrjana ok, I see. Even if CI checks against master, PR can still be out dated with new patches merged into master. I'm overthinking.

[mrjana]

You need to update the .PHONY target line above with this target Otherwise it is going to create an empty file calleed start-services in the root directory.

[mrjana]

@chenchun Thanks for taking care of the comments. LGTM

[mavenugo]

👍