Let name server generate valid JSON response when process topic route queries

[lizhanhui]

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[coveralls]

Coverage increased (+0.03%) to 52.064% when pulling 4d112dc on lizhanhui:apache_develop into aacaf91 on apache:develop.

[codecov-commenter]

Codecov Report

Merging #4432 (d01b04f) into develop (aacaf91) will decrease coverage by 0.09%.
The diff coverage is 100.00%.

@@              Coverage Diff              @@
##             develop    #4432      +/-   ##
=============================================
- Coverage      48.14%   48.05%   -0.10%     
+ Complexity      5108     5092      -16     
=============================================
  Files            646      646              
  Lines          42909    42911       +2     
  Branches        5611     5611              
=============================================
- Hits           20658    20620      -38     
- Misses         19743    19774      +31     
- Partials        2508     2517       +9     

Impacted Files	Coverage Δ
...tmq/namesrv/processor/DefaultRequestProcessor.java	73.58% <100.00%> (ø)
...cketmq/remoting/protocol/RemotingSerializable.java	77.77% <100.00%> (+15.27%)	⬆️
...rg/apache/rocketmq/common/stats/StatsSnapshot.java	84.61% <0.00%> (-15.39%)	⬇️
.../apache/rocketmq/common/stats/MomentStatsItem.java	38.09% <0.00%> (-9.53%)	⬇️
...ache/rocketmq/common/stats/MomentStatsItemSet.java	39.13% <0.00%> (-8.70%)	⬇️
...va/org/apache/rocketmq/logging/inner/Appender.java	29.21% <0.00%> (-7.87%)	⬇️
...org/apache/rocketmq/common/stats/StatsItemSet.java	41.79% <0.00%> (-5.98%)	⬇️
...va/org/apache/rocketmq/common/stats/StatsItem.java	50.00% <0.00%> (-5.00%)	⬇️
...lient/impl/consumer/DefaultMQPushConsumerImpl.java	40.84% <0.00%> (-3.00%)	⬇️
...ketmq/common/protocol/body/RegisterBrokerBody.java	84.78% <0.00%> (-1.09%)	⬇️
... and 16 more

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[hzh0425]

Maybe you should adjust the import order

[lizhanhui]

Looks feature 'optimize-import-on-fly' of Idea is not perfect. Reverted.

[hzh0425]

LGTM