tmnxSSHServerPreserveKey specifies the persistence of the SSH
server host key. A value of 'true' specifies that the host key
will be saved by the server and restored following a system
reboot. The SSH client also saves the host key and
restores it following a system reboot.
A value of 'false' specifies that the host key will be held
in memory by both the SSH server and the SSH client and
is not restored following a system reboot.