Fixed the cleanup failure (#7007)

If all the clusters are cleaned up then .clusters.swp
file is not created and it gives an error that file
not present.

Signed-off-by: Pulkit Jain <pulkit.jain@broadcom.com>

ci/kind/kind-setup.sh

@@ -565,6 +565,7 @@ function clean_kind {
       flock -x 200
 
       current_timestamp=$(date +%s)
+      touch ~/.antrea/.clusters.swp
       while IFS=' ' read -r name creationTimestamp; do
           if [[ -z "$name" || -z "$creationTimestamp" ]]; then
               continue