Description of problem:
After configure egressIP, outgoing traffic broke

Version-Release number of selected component (if applicable):
4.6.0-0.nightly-2020-09-10-195619

How reproducible:
Always

Steps to Reproduce:
1.Label one node to be egressIP node
oc label node compute-1 "k8s.ovn.org/egress-assignable"=""

2.
 Create ns test and pods in it.
oc label ns test team=red

oc get pods -o wide -n test
NAME            READY   STATUS    RESTARTS   AGE   IP             NODE        NOMINATED NODE   READINESS GATES
hello-pod       1/1     Running   0          15m   10.128.2.100   compute-0   <none>           <none>
test-rc-mks8g   1/1     Running   0          18s   10.128.2.106   compute-0   <none>           <none>
test-rc-t26dw   1/1     Running   0          17s   10.131.0.9     compute-1   <none>           <none>

3. Apply egressIP object
apiVersion: k8s.ovn.org/v1
kind: EgressIP
metadata:
  name: egressip
spec:
  egressIPs:
  - 139.178.76.20 
  namespaceSelector:
    matchLabels:
      team: red

oc get egressip
NAME       EGRESSIPS       ASSIGNED NODE   ASSIGNED EGRESSIPS
egressip   139.178.76.20   compute-1       139.178.76.20

4. From test pods to access outside websites.



Actual results:
oc rsh -n test hello-pod     
/ # curl ifconfig.me --connect-timeout 5
curl: (7) Failed to connect to ifconfig.me port 80: Operation timed out
/ # 

without patch egressIP, the outgoing traffic works
oc rsh -n test hello-pod
~ $ curl ifconfig.me
139.178.76.9~ $ exit

Expected results:
The outgoing traffic should work with egressIP as source IP



Additional info: