SCB-393 Retry to request etcd too frequently when fail

[little-cui]

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[coveralls]

Coverage decreased (-0.2%) to 73.206% when pulling c7f9bad on little-cui:master into 3618245 on apache:master.

[codecov-io]

Codecov Report

Merging #352 into master will decrease coverage by 0.24%.
The diff coverage is 97.43%.

@@            Coverage Diff             @@
##           master     #352      +/-   ##
==========================================
- Coverage   69.88%   69.64%   -0.25%     
==========================================
  Files          18       18              
  Lines        3420     3406      -14     
==========================================
- Hits         2390     2372      -18     
- Misses        865      868       +3     
- Partials      165      166       +1

Impacted Files	Coverage Δ
server/service/instances.go	68.58% <ø> (-2.56%)	⬇️
server/service/util/heartbeat_util.go	80% <100%> (ø)	⬆️
server/service/microservices.go	74.55% <100%> (ø)	⬆️
server/service/util/tag_util.go	65.51% <100%> (ø)	⬆️
server/service/util/dependency.go	56.37% <100%> (ø)	⬆️
server/service/schema.go	75% <100%> (ø)	⬆️
server/service/util/microservice_util.go	74.84% <100%> (ø)	⬆️
server/service/util/domain_util.go	71.64% <100%> (ø)	⬆️
server/service/util/schema_util.go	87.5% <100%> (ø)	⬆️
server/service/util/rule_util.go	67.5% <100%> (ø)	⬆️
... and 2 more

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