Ftr: protocol_conf default values

[joeyzhouy]

Ftr: issue #215

[codecov-io]

Codecov Report

Merging #221 into develop will decrease coverage by 1.59%.
The diff coverage is 4.76%.

@@            Coverage Diff             @@
##           develop     #221     +/-   ##
==========================================
- Coverage    66.11%   64.52%   -1.6%     
==========================================
  Files           95       95             
  Lines         6511     6563     +52     
==========================================
- Hits          4305     4235     -70     
- Misses        1765     1892    +127     
+ Partials       441      436      -5

Impacted Files	Coverage Δ
protocol/dubbo/config.go	14.28% <0%> (-27.39%)	⬇️
protocol/dubbo/client.go	68.87% <10.52%> (-2.08%)	⬇️
protocol/dubbo/server.go	62.65% <10.52%> (-3.6%)	⬇️
cluster/cluster_impl/base_cluster_invoker.go	54.71% <0%> (-16.99%)	⬇️
protocol/dubbo/pool.go	57.86% <0%> (-15.74%)	⬇️
protocol/dubbo/listener.go	51.19% <0%> (-13.7%)	⬇️
protocol/dubbo/codec.go	76.47% <0%> (-5.89%)	⬇️
protocol/dubbo/readwriter.go	67.9% <0%> (-2.47%)	⬇️
remoting/zookeeper/listener.go	46.9% <0%> (-1.04%)	⬇️
registry/etcdv3/registry.go	50.5% <0%> (-1.02%)	⬇️
... and 3 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ab77c92...7ad6b3d. Read the comment docs.

[AlexStocks]

@fangyincheng pls check this pr. if there is no problems, u can merge it.

[fangyincheng]

LGTM