bugfix:code optimization of EurekaRegistryServiceImpl

[xingfudeshi]

Ⅰ. Describe what this PR did

1.Remove redundant static keywords
2.initial size of map.
3.lazy load of some object.

Ⅱ. Does this pull request fix one issue?

#753

Ⅲ. Why don't you add test cases (unit test/integration test)?

I've done integration testing.

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[codecov-io]

Codecov Report

Merging #754 into develop will not change coverage.
The diff coverage is 0%.

@@            Coverage Diff             @@
##             develop     #754   +/-   ##
==========================================
  Coverage      32.25%   32.25%           
  Complexity       926      926           
==========================================
  Files            228      228           
  Lines           9058     9058           
  Branches        1102     1101    -1     
==========================================
  Hits            2922     2922           
  Misses          5788     5788           
  Partials         348      348

Impacted Files	Coverage Δ	Complexity Δ
.../discovery/registry/EurekaRegistryServiceImpl.java	0% <0%> (ø)	0 <0> (ø)	⬇️
.../alibaba/fescar/config/ZookeeperConfiguration.java	0% <0%> (ø)	0 <0> (ø)	⬇️

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[slievrly]

LGTM

[zhangthen]

+1