Flaky TestReloader_ConfigDirApplyBasedOnWatchInterval

[GiedriusS]

Flaky test:

 --- FAIL: TestReloader_ConfigDirApplyBasedOnWatchInterval (1.51s)
    reloader_test.go:720: Performing step number 0
    reloader_test.go:720: Performing step number 1
    reloader_test.go:720: Performing step number 3
    testutil.go:91: reloader_test.go:782: ""
        
        	exp: 2
        
        	got: 3
        
FAIL
FAIL	github.com/thanos-io/thanos/pkg/reloader	12.952s

[Saumya40-codes]

Its seems to be happening when both of the following changes are being considered as different (we expect it to be single event. (thus frequency of this test failing is also very low !?)

case 0:

  testutil.Ok(t, os.Symlink(path.Join(dir2, "rule3-001.yaml"), path.Join(dir2, "rule3.yaml")))
  testutil.Ok(t, os.Rename(path.Join(dir2, "rule3.yaml"), path.Join(dir, "rule3.yaml")))

maybe we can use mutex to stop this from happening (but does that might defeat the purpose?) or handle the two code lines seperately here