[Fix]fix dubbo group issues#238

[apollo-go]

What this PR does:

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[codecov-io]

Codecov Report

Merging #243 into master will decrease coverage by 0.08%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #243      +/-   ##
==========================================
- Coverage   64.59%   64.51%   -0.09%     
==========================================
  Files          95       95              
  Lines        6570     6571       +1     
==========================================
- Hits         4244     4239       -5     
- Misses       1888     1894       +6     
  Partials      438      438

Impacted Files	Coverage Δ
protocol/dubbo/client.go	69.07% <100%> (+0.2%)	⬆️
cluster/cluster_impl/base_cluster_invoker.go	54.71% <0%> (-16.99%)	⬇️
config_center/zookeeper/listener.go	82.6% <0%> (-4.35%)	⬇️
remoting/zookeeper/client.go	64.45% <0%> (+0.57%)	⬆️
remoting/zookeeper/listener.go	47.93% <0%> (+1.03%)	⬆️

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[AlexStocks]

LGTM

[AlexStocks]

@apollo-go pls change the target branch to develop. thx.

[fangyincheng]

LGTM

[fangyincheng]

@apollo-go pls change the target branch to develop. thx.

I think a bug should be merged to branch master, and create a pr to branch develop again.