Set SSH default port to 22

If nothing is configured, the advertised ssh address is *:29418, and it
is translated to host:29418.

If sshd.listenAddress is configured without a port, then the advertised
address is host:29418.

If it is configured with port 22, the advertised address is host, without
the port.

The logic in SshScheme assumed that "no port" is 29418, which is
incorrect.

Change-Id: I8b4717a1f5765272b4c3bd7683750ae8fd12a4d5