etcd3 integration test api

[Moriadry-zz]

What is the purpose of the change

fix #3631

Brief changelog

XXXXX

Verifying this change

XXXXX

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[codecov-io]

Codecov Report

Merging #3887 into master will decrease coverage by 0.09%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##             master    #3887     +/-   ##
===========================================
- Coverage     63.77%   63.67%   -0.1%     
  Complexity       71       71             
===========================================
  Files           712      713      +1     
  Lines         31450    31455      +5     
  Branches       5073     5070      -3     
===========================================
- Hits          20057    20029     -28     
- Misses         9103     9131     +28     
- Partials       2290     2295      +5

Impacted Files	Coverage Δ	Complexity Δ
.../apache/dubbo/qos/protocol/QosProtocolWrapper.java	69.23% <0%> (-12.83%)	0% <0%> (ø)
...ache/dubbo/remoting/p2p/support/AbstractGroup.java	45.45% <0%> (-11.37%)	0% <0%> (ø)
...apache/dubbo/common/config/ConfigurationUtils.java	64% <0%> (-8%)	0% <0%> (ø)
...ava/org/apache/dubbo/config/DubboShutdownHook.java	75% <0%> (-6.25%)	0% <0%> (ø)
.../apache/dubbo/remoting/transport/AbstractPeer.java	63.04% <0%> (-4.35%)	0% <0%> (ø)
...e/dubbo/remoting/transport/netty4/NettyClient.java	70.58% <0%> (-4.02%)	0% <0%> (ø)
...pache/dubbo/registry/support/AbstractRegistry.java	78.92% <0%> (-3.07%)	0% <0%> (ø)
...dubbo/remoting/exchange/support/DefaultFuture.java	73.46% <0%> (-2.73%)	0% <0%> (ø)
.../exchange/support/header/HeaderExchangeServer.java	66.98% <0%> (-1.89%)	0% <0%> (ø)
.../java/org/apache/dubbo/config/ReferenceConfig.java	60.14% <0%> (-1.09%)	0% <0%> (ø)
... and 10 more

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[Moriadry-zz]

@zonghaishang hi, could pls help check this, many thanks :)

[ralf0131]

LGTM. Thanks for the pull request.

You can further improve to the org.apache.dubbo.remoting.etcd.jetcd.JEtcdClientTest and org.apache.dubbo.remoting.etcd.jetcd.JEtcdClientWrapperTest, which are both disabled!

I will merge this pull request. You can create a new pr to fix it.

[Moriadry-zz]

Sure, thank you for your help.