To verify that the sftp server is actually running, responsive and that

To verify that the sftp server is actually running, responsive and that
all curl's tests generated configuration and key files are fine, a real
connection is established to the test harness sftp server authenticating
and running a simple sftp remote pwd command.

The verification is done using OpenSSH's or SunSSH's sftp client tool with
a configuration file with the same options as the test harness socks server
with the exception that dynamic forwarding is not used for sftp.