fix: polaris registry bug: nodes is empty at startup

[libi]

Description (what this PR does / why we need it):

北极星服务发现基本不可用,在项目初始化时如果依赖的服务节点没有变化(推送watch),那么Next()函数会阻塞,导致后启动的服务获取不到其他节点信息.

Which issue(s) this PR fixes (resolves / be part of):

Other special notes for the reviewers:

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (a556a2b) 84.62% compared to head (134cde6) 84.72%.

❗ Current head 134cde6 differs from pull request most recent head 889ac7e. Consider uploading reports for the commit 889ac7e to get more accurate results

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3160      +/-   ##
==========================================
+ Coverage   84.62%   84.72%   +0.10%     
==========================================
  Files          88       88              
  Lines        3993     3993              
==========================================
+ Hits         3379     3383       +4     
+ Misses        440      438       -2     
+ Partials      174      172       -2     

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