Cannot use Windows domain account for WinRM with SSH jump station

[vpartington]

When connecting to a target WinRM machine through an SSH tunnel with a Windows domain account, the SPN for which a Kerberos ticket is requested is wrong (localhost instead of the actual hostname). That causes authentication to fail with the following error logged on WARN:

KERBEROS authentication error: No valid credentials provided (Mechanism level: Server not found in Kerberos database (7))