Describe the bug
TestNetworkPolicyMetrics failed on an irrelevant PR vmware-tanzu/antrea#1389, and race was detected:

2020-10-15T09:14:50.3969191Z --- FAIL: TestNetworkPolicyMetrics (0.05s)
2020-10-15T09:14:50.3989561Z     networkpolicy_controller_test.go:528: 
2020-10-15T09:14:50.3990066Z         	Error Trace:	networkpolicy_controller_test.go:528
2020-10-15

Device plugin image is currently Fedora with OVS client and iproute. This could be improved using thinner clients and maybe even Alpine linux.