Do not load unnecessary images in ci/kind/test-upgrade-antrea.sh (#6039)

In particular, when testing upgrade from a minor version already using
split images (e.g., 1.15.0), we should not pull the unified image and
load it into the K8s Nodes, as it won't be used.

This should help reduce disk usage of the Kind cluster in CI.

Signed-off-by: Antonin Bas <antonin.bas@broadcom.com>

ci/kind/test-upgrade-antrea.sh

@@ -148,8 +148,18 @@ fi
 
 echo "Running upgrade test for tag $FROM_TAG"
 
-DOCKER_IMAGES=("busybox" "projects.registry.vmware.com/antrea/antrea-ubuntu:$FROM_TAG")
+function version_lt() { test "$(printf '%s\n' "$@" | sort -rV | head -n 1)" != "$1"; }
+
+DOCKER_IMAGES=()
+if version_lt "$FROM_TAG" v1.15; then
+    DOCKER_IMAGES+=("projects.registry.vmware.com/antrea/antrea-ubuntu:$FROM_TAG")
+else
+    DOCKER_IMAGES+=("projects.registry.vmware.com/antrea/antrea-agent-ubuntu:$FROM_TAG" \
+                    "projects.registry.vmware.com/antrea/antrea-controller-ubuntu:$FROM_TAG")
+fi
 
+# Silence CLI suggestions.
+export DOCKER_CLI_HINTS=false
 for img in "${DOCKER_IMAGES[@]}"; do
     echo "Pulling $img"
     for i in `seq 3`; do