configure the server side's long polling timeout

[crecel]

related pr: #2523

[codecov-io]

Codecov Report

Merging #2532 into master will decrease coverage by 0.02%.
The diff coverage is 60%.

@@             Coverage Diff              @@
##             master    #2532      +/-   ##
============================================
- Coverage     50.19%   50.16%   -0.03%     
+ Complexity     2046     2045       -1     
============================================
  Files           410      410              
  Lines         12554    12556       +2     
  Branches       1285     1285              
============================================
- Hits           6301     6299       -2     
- Misses         5806     5809       +3     
- Partials        447      448       +1

Impacted Files	Coverage Δ	Complexity Δ
...m/ctrip/framework/apollo/biz/config/BizConfig.java	31.25% <0%> (-1.36%)	8 <0> (ø)
...o/configservice/wrapper/DeferredResultWrapper.java	100% <100%> (ø)	12 <1> (ø)	⬇️
...igservice/controller/NotificationControllerV2.java	86.2% <100%> (ø)	31 <0> (ø)	⬇️
.../apollo/internals/RemoteConfigLongPollService.java	79.01% <0%> (-1.24%)	27% <0%> (-1%)

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[coveralls]

Coverage decreased (-0.02%) to 53.735% when pulling 98712ee on crecel:crecel-branch into cbb6d7d on ctripcorp:master.

[JaredTan95]

LGTM

[freshgeek]

this env is add in apollo server start ? long.polling.timeout

[nobodyiam]

You may add it in the system config page.