Optimize code and improve readability #157

Job	Run time
set-execution-conditions	13s
build agent and cache	5m 54s
download midwares and cache	5s
Test for xds service discovery with spring-server using envoy	3m 35s
Test for agentcore dynamic config (127.0.0.1:8848, NACOS)	1m 15s
Test for xds service discovery with only sermant	4m 12s
Test for agentcore dynamic config (127.0.0.1:2181, ZOOKEEPER)	1m 1s
Test for xds router and lb with router plugin (2.0.2.RELEASE, 1.19, Finchley.RELEASE, 4.4, 2.2.0,...	5m 44s
Test for xds service discovery with spring-client using enovy	3m 43s
Test for xds router and lb with router plugin (2.1.0.RELEASE, 1.23, Greenwich.RELEASE, 4.4.1, 2.3...	6m 15s
Test for xds router and lb with router plugin (2.2.0.RELEASE, 1.25, Hoxton.RELEASE, 4.5, 2.4.0, 3...	5m 43s
Test for xds router and lb with router plugin (2.3.0.RELEASE, 1.26, Hoxton.RELEASE, 4.5.3, 2.5.0,...	5m 58s
Test for xds router and lb with router plugin (2.4.0, 1.27, 2020.0.0, 4.5.7, 2.6.0, 4.2.2, 4.1.2)	5m 15s
Test for xds router and lb with router plugin (2.6.2, 1.29, 2021.0.0, 4.5.10, 2.7.3, 4.7.2, 4.1.3)	5m 23s
Test for xds router and lb with router plugin (2.7.17, 1.30, 2021.0.3, 4.5.13, 2.7.5, 4.12.0, 4.1.5)	5m 43s
	59m 59s

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