do not copy any existing SSH host keys into the target Haiku filesystem

[dovsienko]

When a user writes the "anyboot" disk image to a USB storage and boots from it, they see an "install Haiku or try Haiku" window. If the user chooses to try Haiku first, this among other things generates host SSH keys and stores these on the USB storage. When the user runs the installer from that USB storage later, the target system has the same SSH host keys, which is not a good practice. The host keys should be omitted (or at least deleted after the installation, if that's easier), so the target system can generate its own keys.