*: update drainExecSyncIO docs and validate the timeout

We should validate the drainExecSyncIO timeout at the beginning and
raise the error for any invalid input.

Signed-off-by: Wei Fu <fuweid89@gmail.com>

pkg/cri/config/config_unix.go

@@ -110,6 +110,6 @@ func DefaultConfig() PluginConfig {
 		EnableCDI:                false,
 		CDISpecDirs:              []string{"/etc/cdi", "/var/run/cdi"},
 		ImagePullProgressTimeout: time.Minute.String(),
-		DrainExecSyncIOTimeout:   "0",
+		DrainExecSyncIOTimeout:   "0s",
 	}
 }