deployment: do not use SSH host key of deployment system

Yak shaving...

From: Michael Prokop <mprokop@sipwise.com>

deployment.sh

@@ -1303,7 +1303,12 @@ if "$PRO_EDITION" ; then
     ngcpcfg commit "deployed /etc/ngcp-config/network.yml on $ROLE"
     ngcpcfg push --shared-only
     ssh-keyscan $PEER >> ~/.ssh/known_hosts
-    ssh $PEER "ssh-keyscan $THIS_HOST >> ~/.ssh/known_hosts"
+
+    # live system uses a different SSH host key than the finally installed
+    # system, so do NOT use ssh-keyscan here
+    SSH_KEY="$(awk '{print $1 " " $2}' /etc/ssh/ssh_host_rsa_key.pub)"
+    ssh $PEER "echo $THIS_HOST \$SSH_KEY >> ~/.ssh/known_hosts"
+
     ssh $PEER ngcpcfg pull
     ngcpcfg build
   fi