Assess workaround options for sshpiper banning user

From the sshpiper debug session last week, we noticed that sshpiper will retry till it gets banned if:

1. user's account is expired
2. user uses key based authentication

Potential options:

1. use ForceCommand exit in sshd_config
2. don't expire user's account

We need to:

1. understand what else does the expired account provides.

Related issue:

• https://github.com/tg123/sshpiper/issues/608