CI: fix the issue of missing 'ps' command in irssi:1 image

The image irssi:1 didn't have 'ps' command, thus using
'whoami' to verify the user.

Signed-off-by: fupan <lifupan@gmail.com>

Author: lifupan

hack/lib/test.sh

@@ -175,7 +175,7 @@ hyper::test::imageuser() {
   echo "Pod image user config test"
   # irssi image has "User": "user"
   id=$(sudo hyperctl run -d --env="TERM=xterm" irssi:1 | sed -ne "s/POD id is \(.*\)/\1/p")
-  res=$(sudo hyperctl exec $id ps aux | grep user > /dev/null 2>&1; echo $?)
+  res=$(sudo hyperctl exec $id whoami | grep user > /dev/null 2>&1; echo $?)
   sudo hyperctl rm $id
   test $res -eq 0
 }