To achieve that, we had to get rid of the seq_command_executed request
parameter. We replaced it by a cookie, which is cleared after the
warning is displayed.
Note that we had to remove a feature, which was to disable/enable all
inputs while commands were running. This was causing very weird
behaviour, where some disabled buttons were being re-enabled again.
We also had to get rid of the cookieStore, which is not compatible with
non-https access. Http access is required in the self-serve AMI, for
instance.
