Fix ci/test-e2e-kind.sh script on macOS (antrea-io#6117)

The script was failing with:
```
Deleting VLAN subnets
Option "-br" is unknown, try "ip help".
```
when cleaning-up a test cluster.

This is because the ip command on macOS only supports a subset of the
command-line options supported on Linux. In any case, on macOS, the
command needs be wrapped with docker_run_with_host_net, since we are
looking for VLAN interfaces running in the Docker Linux VM.

As a minor improvement, we also add the "antrea" prefix to the external
server container we create, along with a short random suffix ($RANDOM is
sufficient for this) to avoid possible conflicts.

Fixes antrea-io#6022

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

ci/kind/kind-setup.sh

@@ -270,7 +270,7 @@ function delete_vlan_subnets {
   bridge_interface="br-${bridge_id:0:12}"
   vlan_interface_prefix="br-${bridge_id:0:7}."
 
-  found_vlan_interfaces=$(ip -br link show type vlan | cut -d " " -f 1)
+  found_vlan_interfaces=$(docker_run_with_host_net ip -br link show type vlan | cut -d " " -f 1)
   for interface in $found_vlan_interfaces ; do
     if [[ $interface =~ ${vlan_interface_prefix}[0-9]+@${bridge_interface} ]]; then
       interface_name=${interface%@*}
@@ -441,9 +441,9 @@ function destroy {
   else
       kind delete cluster --name $CLUSTER_NAME
   fi
+  destroy_external_server
   delete_networks
   delete_vlan_subnets
-  destroy_external_server
 }
 
 function printUnixTimestamp {
@@ -457,13 +457,14 @@ function printUnixTimestamp {
 
 function setup_external_server {
   if [[ $DEPLOY_EXTERNAL_SERVER == true ]]; then
-    docker run -d --name external-server --network kind -it --rm registry.k8s.io/e2e-test-images/agnhost:2.29 netexec &> /dev/null
+    docker run -d --name antrea-external-server-$RANDOM --network kind -it --rm registry.k8s.io/e2e-test-images/agnhost:2.29 netexec &> /dev/null
   fi
 }
 
 function destroy_external_server {
   echo "Deleting external server"
-  docker rm -f external-server &> /dev/null || true
+  cid=$(docker ps -f name="^antrea-external-server" --format '{{.ID}}')
+  docker rm -f $cid &> /dev/null || true
 }
 
 function clean_kind {
@@ -643,7 +644,7 @@ fi
 
 if [[ $ACTION == "destroy" ]]; then
       destroy
-      exit 0
+      exit
 fi
 
 if [[ -n "$VLAN_SUBNETS" || -n "$VLAN_ID" ]]; then

ci/kind/test-e2e-kind.sh

@@ -364,7 +364,9 @@ function run_test {
     RUN_OPT="-run $run"
   fi
 
-  EXTRA_ARGS="$vlan_args --external-server-ips $(docker inspect external-server -f '{{.NetworkSettings.Networks.kind.IPAddress}},{{.NetworkSettings.Networks.kind.GlobalIPv6Address}}')"
+  external_server_cid=$(docker ps -f name="^antrea-external-server" --format '{{.ID}}')
+  external_server_ips=$(docker inspect $external_server_cid -f '{{.NetworkSettings.Networks.kind.IPAddress}},{{.NetworkSettings.Networks.kind.GlobalIPv6Address}}')
+  EXTRA_ARGS="$vlan_args --external-server-ips $external_server_ips"
 
   go test -v -timeout=$timeout $RUN_OPT antrea.io/antrea/test/e2e $flow_visibility_args -provider=kind --logs-export-dir=$ANTREA_LOG_DIR --skip-cases=$skiplist $coverage_args $EXTRA_ARGS
 }