TestServerRegister is flaky

[rleungx]

Flaky Test

Which jobs are failing

--- FAIL: TestServerRegisterTestSuite (4.51s)
    --- FAIL: TestServerRegisterTestSuite/TestServerRegister (0.37s)
        register_test.go:102: 
            	Error Trace:	/home/runner/work/pd/pd/tests/integrations/mcs/discovery/register_test.go:102
            	            				/home/runner/work/pd/pd/tests/integrations/mcs/discovery/register_test.go:76
            	Error:      	Not equal: 
            	            	expected: "http://127.0.0.1:34041/"
            	            	actual  : "http://127.0.0.1:43241/"
            	            	
            	            	Diff:
            	            	--- Expected
            	            	+++ Actual
            	            	@@ -1 +1 @@
            	            	-http://127.0.0.1:34041/
            	            	+http://127.0.0.1:43241/
            	Test:       	TestServerRegisterTestSuite/TestServerRegister
FAIL

CI link

https://github.com/tikv/pd/actions/runs/4729975009/jobs/8393103620?pr=6330

Reason for failure (if possible)

Anything else