Automated cherry pick of #2730: Fix panic bug in Antrea Policy

[wenyingd]

Cherry pick of #2730 on release-1.2.

#2730: Fix panic bug in Antrea Policy

For details on the cherry pick process, see the cherry pick requests page.

[wenyingd]

/test-all
/test-ipv6-all
/test-ipv6-only-all

[codecov-commenter]

Codecov Report

Merging #2758 (6c7b8c2) into release-1.2 (6d7478f) will decrease coverage by 3.58%.
The diff coverage is 50.00%.

@@               Coverage Diff               @@
##           release-1.2    #2758      +/-   ##
===============================================
- Coverage        60.12%   56.53%   -3.59%     
===============================================
  Files              284      284              
  Lines            22385    24748    +2363     
===============================================
+ Hits             13458    13991     +533     
- Misses            7493     9276    +1783     
- Partials          1434     1481      +47     

Flag	Coverage Δ
e2e-tests	13.06% <0.00%> (?)
kind-e2e-tests	47.15% <0.00%> (+0.02%)	⬆️
unit-tests	42.52% <70.00%> (+0.33%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
pkg/agent/openflow/network_policy.go	71.77% <50.00%> (-4.30%)	⬇️
pkg/ovs/openflow/default.go	50.00% <0.00%> (-50.00%)	⬇️
pkg/util/runtime/runtime.go	50.00% <0.00%> (-50.00%)	⬇️
pkg/ovs/ovsconfig/default.go	50.00% <0.00%> (-50.00%)	⬇️
pkg/controller/types/networkpolicy.go	50.00% <0.00%> (-50.00%)	⬇️
pkg/agent/config/traffic_encap_mode.go	60.86% <0.00%> (-39.14%)	⬇️
pkg/util/sets/string.go	61.53% <0.00%> (-38.47%)	⬇️
pkg/agent/config/node_config.go	63.63% <0.00%> (-36.37%)	⬇️
pkg/agent/proxy/service.go	64.28% <0.00%> (-35.72%)	⬇️
pkg/apis/controlplane/v1beta2/sets.go	37.87% <0.00%> (-23.10%)	⬇️
... and 205 more

[wenyingd]

/test-all
/test-ipv6-all
/test-ipv6-only-all

[wenyingd]

/test-e2e
/test-ipv6-only-conformance
/test-windows-conformance
/test-windows-networkpolicy