Upgrade default K8s version tested in eks (#3695)

1.17 is no longer supported in EKS, upgrade the version to 1.21.

Update the version information for AKS and GKE.

Signed-off-by: Quan Tian <qtian@vmware.com>

ci/jenkins/README.md

@@ -142,23 +142,23 @@ DOCKER_REGISTRY="$(head -n1 ci/docker-registry)"
 
   |  K8s Version |    Node Type    |  Node AMI Family |  Status  |
   | :----------: | :-------------: | :--------------: | :------: |
-  |     1.17     |  EC2 t3.medium  |   AmazonLinux2   |[![Build Status](http://jenkins.antrea-ci.rocks/buildStatus/icon?job=cloud-antrea-eks-conformance-net-policy)](http://jenkins.antrea-ci.rocks/view/cloud/job/cloud-antrea-eks-conformance-net-policy/)|
+  |     1.21     |  EC2 t3.medium  |   AmazonLinux2   |[![Build Status](http://jenkins.antrea-ci.rocks/buildStatus/icon?job=cloud-antrea-eks-conformance-net-policy)](http://jenkins.antrea-ci.rocks/view/cloud/job/cloud-antrea-eks-conformance-net-policy/)|
 
 * [GKE conformance/network policy [bi-daily]](http://jenkins.antrea-ci.rocks/view/cloud/job/cloud-antrea-gke-conformance-net-policy/)
   community tests on GKE cluster using sonobuoy, focusing on "Conformance" and "Feature:NetworkPolicy", skipping the same regexes as in job __conformance__ above.\
   Current test environment matrix:
 
   |  K8s Version   |     Node OS     | VPC Native Mode (on by default) |  Status  |
   | :------------: | :-------------: | :-----------------------------: |:-------: |
-  |    1.17.12     |     Ubuntu      |  On                             |[![Build Status](http://jenkins.antrea-ci.rocks/buildStatus/icon?job=cloud-antrea-gke-conformance-net-policy)](http://jenkins.antrea-ci.rocks/view/cloud/job/cloud-antrea-gke-conformance-net-policy/)|
+  |    1.21.6      |     Ubuntu      |  On                             |[![Build Status](http://jenkins.antrea-ci.rocks/buildStatus/icon?job=cloud-antrea-gke-conformance-net-policy)](http://jenkins.antrea-ci.rocks/view/cloud/job/cloud-antrea-gke-conformance-net-policy/)|
 
 * [AKS conformance/network policy [bi-daily]](http://jenkins.antrea-ci.rocks/view/cloud/job/cloud-antrea-aks-conformance-net-policy/)
   community tests on AKS cluster using sonobuoy, focusing on "Conformance" and "Feature:NetworkPolicy", skipping the same regexes as in job __conformance__ above.\
   Current test environment matrix:
 
   |  K8s Version   |  Node Type          |  Node OS        |  Status  |
   | :------------: | :-----------------: | :-------------: | :------: |
-  |    1.19.9      |  Standard_DS2_v2    |  Ubuntu 18.04   |[![Build Status](http://jenkins.antrea-ci.rocks/buildStatus/icon?job=cloud-antrea-aks-conformance-net-policy)](http://jenkins.antrea-ci.rocks/view/cloud/job/cloud-antrea-aks-conformance-net-policy/)|
+  |    1.21.7      |  Standard_DS2_v2    |  Ubuntu 18.04   |[![Build Status](http://jenkins.antrea-ci.rocks/buildStatus/icon?job=cloud-antrea-aks-conformance-net-policy)](http://jenkins.antrea-ci.rocks/view/cloud/job/cloud-antrea-aks-conformance-net-policy/)|
 
 * [daily-elk-flow-collector-validate](https://jenkins.antrea-ci.rocks/job/antrea-daily-elk-flow-collector-validate-for-period/):
   [![Build Status](http://jenkins.antrea-ci.rocks/buildStatus/icon?job=antrea-daily-elk-flow-collector-validate-for-period)](http://jenkins.antrea-ci.rocks/view/cloud/job/antrea-daily-elk-flow-collector-validate-for-period/)

ci/test-conformance-eks.sh

@@ -21,7 +21,7 @@ function echoerr {
 }
 
 REGION="us-east-2"
-K8S_VERSION="1.17"
+K8S_VERSION="1.21"
 AWS_NODE_TYPE="t3.medium"
 SSH_KEY_PATH="$HOME/.ssh/id_rsa.pub"
 SSH_PRIVATE_KEY_PATH="$HOME/.ssh/id_rsa"