cni:fix order dependent test failures (#28349)
cni:fix order dependent test failures (#28349)

The `interceptRuleMgrType` decalred in main.go as "iptables", it would
be changed to "mock" in func resetGlobalTestVariables().

When run single test, it would be "iptables" and make test failed.

Signed-off-by: Xiang Dai <c54c64cf7043291b886753756d851be401eacd91@foxmail.com>
istio/istio,istio/istio,istio/istio,istio/istio,istio/istio