oeqa/runtime/rpm: ensure no user process running before deleting user
In case of systemd, `su -c 'xxx' test1' via ssh will create
several processes owned by test1, e.g. /lib/system/systemd --user.
These processes are actually managed by user@UID.service
(e.g. user@1000.service). And such service is managed
automatically by systemd. In other words, it will be cleaned
up by systemd automatically.
So we need to wait for systemd to clean it up before trying to
use `userdel' to delete the user.
Signed-off-by: Chen Qi <Qi.Chen@windriver.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
