优化kubernetes去掉nodeSelector,使用POD反亲和性(podAntiAffinity)将同一个服务的POD分散在不同的主机或者拓扑域中，提高服务本身的稳定性。

[Hwting]

nodeSelector只能提供简单的将pod限制为具有特定标签的节点,而podAntiAffinity将同一个服务的POD分散在不同的主机或者拓扑域中，提高服务本身的稳定性。
官方文档：https://kubernetes.io/docs/concepts/configuration/assign-pod-node/

[codecov-io]

Codecov Report

Merging #2398 into master will increase coverage by 7.93%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #2398      +/-   ##
============================================
+ Coverage     50.21%   58.15%   +7.93%     
+ Complexity     2027     1162     -865     
============================================
  Files           407      196     -211     
  Lines         12457     5943    -6514     
  Branches       1278      636     -642     
============================================
- Hits           6255     3456    -2799     
+ Misses         5756     2223    -3533     
+ Partials        446      264     -182

Impacted Files	Coverage Δ	Complexity Δ
...work/apollo/biz/message/DatabaseMessageSender.java	56.25% <0%> (-10.42%)	6% <0%> (-2%)
.../apollo/internals/RemoteConfigLongPollService.java	79.01% <0%> (-1.24%)	27% <0%> (-1%)
.../portal/spi/configuration/LdapGroupProperties.java
...ework/apollo/portal/controller/ItemController.java
...o/configservice/wrapper/DeferredResultWrapper.java
...omponent/emailbuilder/GrayPublishEmailBuilder.java
...k/apollo/portal/controller/FavoriteController.java
...apollo/portal/entity/vo/AppRolesAssignedUsers.java
...ponent/emailbuilder/NormalPublishEmailBuilder.java
.../framework/apollo/portal/entity/vo/SystemInfo.java
... and 203 more

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[nobodyiam]

LGTM