host-deploy: add host ssh fingerprint to registration protocol

This is required to allow secure call back into node and avoid man in
the middle, we can now do this.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1090168
Change-Id: I1a9af59277b5055453159f002f19046c0051d82f
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>